From f9f104a4f8468f47cce9408af59398707bc61c83 Mon Sep 17 00:00:00 2001
From: Anders Kaseorg <anders@zulipchat.com>
Date: Fri, 1 Nov 2019 16:06:25 -0700
Subject: [PATCH] js: Automatically convert var to let and const in more files.

This commit was automatically generated by `tools/lint --only=eslint
--fix`, after an `.eslintrc.json` change.

A half dozen files were removed from the changes by tabbott pending
further work to ensure we avoid breaking valuable PRs with merge
conflicts.

Signed-off-by: Anders Kaseorg <anders@zulipchat.com>
---
 frontend_tests/node_tests/buddy_data.js       |  10 +-
 frontend_tests/node_tests/filter.js           |  82 ++---
 frontend_tests/node_tests/markdown.js         |  68 ++--
 .../node_tests/settings_user_groups.js        | 234 ++++++-------
 frontend_tests/node_tests/templates.js        |   6 +-
 static/js/buddy_data.js                       |  64 ++--
 static/js/click_handlers.js                   | 154 ++++-----
 static/js/copy_and_paste.js                   |  70 ++--
 static/js/hash_util.js                        |  34 +-
 static/js/message_list_view.js                | 276 +++++++--------
 static/js/narrow.js                           | 158 ++++-----
 static/js/popovers.js                         | 316 +++++++++---------
 static/js/settings_org.js                     |   4 +-
 static/js/settings_user_groups.js             |  90 ++---
 static/js/stream_create.js                    |  96 +++---
 static/js/subs.js                             | 140 ++++----
 tools/webpack-helpers.ts                      |   4 +-
 tools/webpack.config.ts                       |   2 +-
 18 files changed, 904 insertions(+), 904 deletions(-)

diff --git a/frontend_tests/node_tests/buddy_data.js b/frontend_tests/node_tests/buddy_data.js
index 9b0cbef727..61793ad666 100644
--- a/frontend_tests/node_tests/buddy_data.js
+++ b/frontend_tests/node_tests/buddy_data.js
@@ -128,9 +128,9 @@ run_test('buddy_status', () => {
 
 run_test('title_data', () => {
     // Groups
-    var is_group = true;
-    var user_ids_string = "9999,1000";
-    var expected_group_data = {
+    let is_group = true;
+    const user_ids_string = "9999,1000";
+    let expected_group_data = {
         is_group: is_group,
         recipients: "Human Selma, Old User",
         is_bot: false,
@@ -140,7 +140,7 @@ run_test('title_data', () => {
     is_group = '';
 
     // Bots with owners.
-    var bot_owner_exists = true;
+    let bot_owner_exists = true;
     expected_group_data = {
         is_group: '',
         name: 'Blue Herring Bot',
@@ -168,7 +168,7 @@ run_test('title_data', () => {
         status_text: 'out to lunch',
     });
 
-    var expected_data = {
+    let expected_data = {
         is_group: is_group,
         status_text: 'out to lunch',
         last_seen: 'translated: Active now',
diff --git a/frontend_tests/node_tests/filter.js b/frontend_tests/node_tests/filter.js
index bb379c88db..8314d3c8b7 100644
--- a/frontend_tests/node_tests/filter.js
+++ b/frontend_tests/node_tests/filter.js
@@ -9,19 +9,19 @@ set_global('message_store', {});
 set_global('page_params', {});
 set_global('feature_flags', {});
 
-var me = {
+const me = {
     email: 'me@example.com',
     user_id: 30,
     full_name: 'Me Myself',
 };
 
-var joe = {
+const joe = {
     email: 'joe@example.com',
     user_id: 31,
     full_name: 'joe',
 };
 
-var steve = {
+const steve = {
     email: 'STEVE@foo.com',
     user_id: 32,
     full_name: 'steve',
@@ -36,7 +36,7 @@ function assert_same_operators(result, terms) {
     terms = _.map(terms, function (term) {
         // If negated flag is undefined, we explicitly
         // set it to false.
-        var negated = term.negated;
+        let negated = term.negated;
         if (!negated) {
             negated = false;
         }
@@ -50,12 +50,12 @@ function assert_same_operators(result, terms) {
 }
 
 run_test('basics', () => {
-    var operators = [
+    let operators = [
         {operator: 'stream', operand: 'foo'},
         {operator: 'stream', operand: 'exclude_stream', negated: true},
         {operator: 'topic', operand: 'bar'},
     ];
-    var filter = new Filter(operators);
+    let filter = new Filter(operators);
 
     assert_same_operators(filter.operators(), operators);
     assert.deepEqual(filter.operands('stream'), ['foo']);
@@ -162,10 +162,10 @@ run_test('basics', () => {
     assert(filter.can_apply_locally());
 });
 run_test('show_first_unread', () => {
-    var operators = [
+    let operators = [
         {operator: 'is', operand: 'any'},
     ];
-    var filter = new Filter(operators);
+    let filter = new Filter(operators);
     assert(filter.allow_use_first_unread_when_narrowing());
 
     operators = [
@@ -188,42 +188,42 @@ run_test('show_first_unread', () => {
 
 });
 run_test('topic_stuff', () => {
-    var operators = [
+    const operators = [
         {operator: 'stream', operand: 'foo'},
         {operator: 'topic', operand: 'old topic'},
     ];
-    var filter = new Filter(operators);
+    const filter = new Filter(operators);
 
     assert(filter.has_topic('foo', 'old topic'));
     assert(!filter.has_topic('wrong', 'old topic'));
     assert(!filter.has_topic('foo', 'wrong'));
 
-    var new_filter = filter.filter_with_new_topic('new topic');
+    const new_filter = filter.filter_with_new_topic('new topic');
 
     assert.deepEqual(new_filter.operands('stream'), ['foo']);
     assert.deepEqual(new_filter.operands('topic'), ['new topic']);
 });
 
 run_test('new_style_operators', () => {
-    var term = {
+    const term = {
         operator: 'stream',
         operand: 'foo',
     };
-    var operators = [term];
-    var filter = new Filter(operators);
+    const operators = [term];
+    const filter = new Filter(operators);
 
     assert.deepEqual(filter.operands('stream'), ['foo']);
     assert(filter.is_exactly('stream'));
 });
 
 run_test('public_operators', () => {
-    var operators = [
+    let operators = [
         {operator: 'stream', operand: 'foo'},
         {operator: 'in', operand: 'all'},
         {operator: 'topic', operand: 'bar'},
     ];
 
-    var filter = new Filter(operators);
+    let filter = new Filter(operators);
     assert_same_operators(filter.public_operators(), operators);
     assert(!filter.is_exactly('stream'));
 
@@ -241,7 +241,7 @@ run_test('canonicalizations', () => {
     assert.equal(Filter.canonicalize_operator('Subject'), 'topic');
     assert.equal(Filter.canonicalize_operator('FROM'), 'sender');
 
-    var term;
+    let term;
     term = Filter.canonicalize_term({operator: 'Stream', operand: 'Denmark'});
     assert.equal(term.operator, 'stream');
     assert.equal(term.operand, 'Denmark');
@@ -292,7 +292,7 @@ function get_predicate(operators) {
 }
 
 function make_sub(name, stream_id) {
-    var sub = {
+    const sub = {
         name: name,
         stream_id: stream_id,
     };
@@ -308,9 +308,9 @@ run_test('predicate_basics', () => {
     // To keep these tests simple, we only pass objects with a few relevant attributes
     // rather than full-fledged message objects.
 
-    var stream_id = 42;
+    const stream_id = 42;
     make_sub('Foo', stream_id);
-    var predicate = get_predicate([['stream', 'Foo'], ['topic', 'Bar']]);
+    let predicate = get_predicate([['stream', 'Foo'], ['topic', 'Bar']]);
 
     assert(predicate({type: 'stream', stream_id: stream_id, topic: 'bar'}));
     assert(!predicate({type: 'stream', stream_id: stream_id, topic: 'whatever'}));
@@ -356,7 +356,7 @@ run_test('predicate_basics', () => {
     predicate = get_predicate([['in', 'all']]);
     assert(predicate({}));
 
-    var unknown_stream_id = 999;
+    const unknown_stream_id = 999;
     predicate = get_predicate([['in', 'home']]);
     assert(!predicate({stream_id: unknown_stream_id, stream: 'unknown'}));
     assert(predicate({type: 'private'}));
@@ -435,10 +435,10 @@ run_test('predicate_basics', () => {
 });
 
 run_test('negated_predicates', () => {
-    var predicate;
-    var narrow;
+    let predicate;
+    let narrow;
 
-    var social_stream_id = 555;
+    const social_stream_id = 555;
     make_sub('social', social_stream_id);
 
     narrow = [
@@ -459,7 +459,7 @@ run_test('negated_predicates', () => {
 run_test('mit_exceptions', () => {
     global.page_params.realm_is_zephyr_mirror_realm = true;
 
-    var predicate = get_predicate([['stream', 'Foo'], ['topic', 'personal']]);
+    let predicate = get_predicate([['stream', 'Foo'], ['topic', 'personal']]);
     assert(predicate({type: 'stream', stream: 'foo', topic: 'personal'}));
     assert(predicate({type: 'stream', stream: 'foo.d', topic: 'personal'}));
     assert(predicate({type: 'stream', stream: 'foo.d', topic: ''}));
@@ -471,7 +471,7 @@ run_test('mit_exceptions', () => {
     assert(predicate({type: 'stream', stream: 'foo', topic: 'bar.d'}));
 
     // Try to get the MIT regex to explode for an empty stream.
-    var terms = [
+    let terms = [
         {operator: 'stream', operand: ''},
         {operator: 'topic', operand: 'bar'},
     ];
@@ -488,7 +488,7 @@ run_test('mit_exceptions', () => {
 });
 
 run_test('predicate_edge_cases', () => {
-    var predicate;
+    let predicate;
     // The code supports undefined as an operator to Filter, which results
     // in a predicate that accepts any message.
     predicate = new Filter().predicate();
@@ -507,11 +507,11 @@ run_test('predicate_edge_cases', () => {
     assert(predicate({}));
 
     // Exercise caching feature.
-    var terms = [
+    const terms = [
         {operator: 'stream', operand: 'Foo'},
         {operator: 'topic', operand: 'bar'},
     ];
-    var filter = new Filter(terms);
+    const filter = new Filter(terms);
     filter.predicate();
     predicate = filter.predicate(); // get cached version
     assert(predicate({type: 'stream', stream: 'foo', topic: 'bar'}));
@@ -519,11 +519,11 @@ run_test('predicate_edge_cases', () => {
 });
 
 run_test('parse', () => {
-    var string;
-    var operators;
+    let string;
+    let operators;
 
     function _test() {
-        var result = Filter.parse(string);
+        const result = Filter.parse(string);
         assert_same_operators(result, operators);
     }
 
@@ -646,8 +646,8 @@ run_test('parse', () => {
 });
 
 run_test('unparse', () => {
-    var string;
-    var operators;
+    let string;
+    let operators;
 
     operators = [
         {operator: 'stream', operand: 'Foo'},
@@ -697,8 +697,8 @@ run_test('unparse', () => {
 });
 
 run_test('describe', () => {
-    var narrow;
-    var string;
+    let narrow;
+    let string;
 
     narrow = [
         {operator: 'streams', operand: 'public'},
@@ -825,10 +825,10 @@ run_test('describe', () => {
 });
 
 run_test('is_functions', () => {
-    var terms = [
+    let terms = [
         {operator: 'stream', operand: 'My Stream'},
     ];
-    var filter = new Filter(terms);
+    let filter = new Filter(terms);
     assert.equal(filter.is_exactly('stream'), true);
     assert.equal(filter.is_exactly('stream', 'topic'), false);
     assert.equal(filter.is_exactly('pm-with'), false);
@@ -995,12 +995,12 @@ run_test('first_valid_id_from', () => {
 });
 
 run_test('update_email', () => {
-    var terms = [
+    const terms = [
         {operator: 'pm-with', operand: 'steve@foo.com'},
         {operator: 'sender', operand: 'steve@foo.com'},
         {operator: 'stream', operand: 'steve@foo.com'}, // try to be tricky
     ];
-    var filter = new Filter(terms);
+    const filter = new Filter(terms);
     filter.update_email(steve.user_id, 'showell@foo.com');
     assert.deepEqual(filter.operands('pm-with'), ['showell@foo.com']);
     assert.deepEqual(filter.operands('sender'), ['showell@foo.com']);
@@ -1013,6 +1013,6 @@ run_test('error_cases', () => {
     // should not be reached unless we break other code.
     people.pm_with_user_ids = function () {};
 
-    var predicate = get_predicate([['pm-with', 'Joe@example.com']]);
+    const predicate = get_predicate([['pm-with', 'Joe@example.com']]);
     assert(!predicate({type: 'private'}));
 });
diff --git a/frontend_tests/node_tests/markdown.js b/frontend_tests/node_tests/markdown.js
index 0d467db398..b26e08573b 100644
--- a/frontend_tests/node_tests/markdown.js
+++ b/frontend_tests/node_tests/markdown.js
@@ -48,16 +48,16 @@ set_global('Image', function () {
 });
 emoji.initialize();
 
-var doc = "";
+const doc = "";
 set_global('document', doc);
 
 set_global('$', global.make_zjquery());
 
 set_global('feature_flags', {local_echo: true});
 
-var people = global.people;
+const people = global.people;
 
-var cordelia = {
+const cordelia = {
     full_name: 'Cordelia Lear',
     user_id: 101,
     email: 'cordelia@zulip.com',
@@ -96,21 +96,21 @@ people.add({
 
 people.initialize_current_user(cordelia.user_id);
 
-var hamletcharacters = {
+const hamletcharacters = {
     name: "hamletcharacters",
     id: 1,
     description: "Characters of Hamlet",
     members: [cordelia.user_id],
 };
 
-var backend = {
+const backend = {
     name: "Backend",
     id: 2,
     description: "Backend team",
     members: [],
 };
 
-var edgecase_group = {
+const edgecase_group = {
     name: "Bobby <h1>Tables</h1>",
     id: 3,
     description: "HTML Syntax to check for Markdown edge cases.",
@@ -121,15 +121,15 @@ global.user_groups.add(hamletcharacters);
 global.user_groups.add(backend);
 global.user_groups.add(edgecase_group);
 
-var stream_data = global.stream_data;
-var denmark = {
+const stream_data = global.stream_data;
+const denmark = {
     subscribed: false,
     color: 'blue',
     name: 'Denmark',
     stream_id: 1,
     is_muted: true,
 };
-var social = {
+const social = {
     subscribed: true,
     color: 'red',
     name: 'social',
@@ -137,14 +137,14 @@ var social = {
     is_muted: false,
     invite_only: true,
 };
-var edgecase_stream = {
+const edgecase_stream = {
     subscribed: true,
     color: 'green',
     name: 'Bobby <h1>Tables</h1>',
     stream_id: 3,
     is_muted: false,
 };
-var edgecase_stream_2 = {
+const edgecase_stream_2 = {
     subscribed: true,
     color: 'yellow',
     name: 'Bobby <h1',
@@ -161,18 +161,18 @@ stream_data.add_sub('Bobby <h1', edgecase_stream_2);
 // Check the default behavior of fenced code blocks
 // works properly before markdown is initialized.
 run_test('fenced_block_defaults', () => {
-    var input = '\n```\nfenced code\n```\n\nand then after\n';
-    var expected = '\n\n<div class="codehilite"><pre><span></span>fenced code\n</pre></div>\n\n\n\nand then after\n\n';
-    var output = fenced_code.process_fenced_code(input);
+    const input = '\n```\nfenced code\n```\n\nand then after\n';
+    const expected = '\n\n<div class="codehilite"><pre><span></span>fenced code\n</pre></div>\n\n\n\nand then after\n\n';
+    const output = fenced_code.process_fenced_code(input);
     assert.equal(output, expected);
 });
 
 markdown.initialize();
 
-var bugdown_data = global.read_fixture_data('markdown_test_cases.json');
+const bugdown_data = global.read_fixture_data('markdown_test_cases.json');
 
 run_test('bugdown_detection', () => {
-    var no_markup = [
+    const no_markup = [
         "This is a plaintext message",
         "This is a plaintext: message",
         "This is a :plaintext message",
@@ -195,7 +195,7 @@ run_test('bugdown_detection', () => {
         "And an avatar !avatar(leo@zulip.com) is here",
     ];
 
-    var markup = [
+    const markup = [
         "Contains a https://zulip.com/image.png file",
         "Contains a https://zulip.com/image.jpg file",
         "https://zulip.com/image.jpg",
@@ -220,7 +220,7 @@ run_test('bugdown_detection', () => {
 });
 
 run_test('marked_shared', () => {
-    var tests = bugdown_data.regular_tests;
+    const tests = bugdown_data.regular_tests;
 
     tests.forEach(function (test) {
 
@@ -229,11 +229,11 @@ run_test('marked_shared', () => {
             return;
         }
 
-        var message = {raw_content: test.input};
+        const message = {raw_content: test.input};
         page_params.translate_emoticons = test.translate_emoticons || false;
         markdown.apply_markdown(message);
-        var output = message.content;
-        var error_message = `Failure in test: ${test.name}`;
+        const output = message.content;
+        const error_message = `Failure in test: ${test.name}`;
         if (test.marked_expected_output) {
             global.bugdown_assert.notEqual(test.expected_output, output, error_message);
             global.bugdown_assert.equal(test.marked_expected_output, output, error_message);
@@ -246,7 +246,7 @@ run_test('marked_shared', () => {
 });
 
 run_test('message_flags', () => {
-    var message = {raw_content: '@**Leo**'};
+    let message = {raw_content: '@**Leo**'};
     markdown.apply_markdown(message);
     assert(!message.mentioned);
     assert(!message.mentioned_me_directly);
@@ -263,7 +263,7 @@ run_test('message_flags', () => {
 });
 
 run_test('marked', () => {
-    var test_cases = [
+    const test_cases = [
         {input: 'hello', expected: '<p>hello</p>'},
         {input: 'hello there', expected: '<p>hello there</p>'},
         {input: 'hello **bold** for you', expected: '<p>hello <strong>bold</strong> for you</p>'},
@@ -396,18 +396,18 @@ run_test('marked', () => {
         // Disable emoji conversion by default.
         page_params.translate_emoticons = test_case.translate_emoticons || false;
 
-        var input = test_case.input;
-        var expected = test_case.expected;
+        const input = test_case.input;
+        const expected = test_case.expected;
 
-        var message = {raw_content: input};
+        const message = {raw_content: input};
         markdown.apply_markdown(message);
-        var output = message.content;
+        const output = message.content;
         assert.equal(expected, output);
     });
 });
 
 run_test('topic_links', () => {
-    var message = {type: 'stream', topic: "No links here"};
+    let message = {type: 'stream', topic: "No links here"};
     markdown.add_topic_links(message);
     assert.equal(util.get_topic_links(message).length, []);
 
@@ -456,8 +456,8 @@ run_test('topic_links', () => {
 });
 
 run_test('message_flags', () => {
-    var input = "/me is testing this";
-    var message = {topic: "No links here", raw_content: input};
+    let input = "/me is testing this";
+    let message = {topic: "No links here", raw_content: input};
     markdown.apply_markdown(message);
 
     assert.equal(message.is_me_message, true);
@@ -528,7 +528,7 @@ run_test('message_flags', () => {
 });
 
 run_test('backend_only_realm_filters', () => {
-    var backend_only_realm_filters = [
+    const backend_only_realm_filters = [
         'Here is the PR-#123.',
         'Function abc() was introduced in (PR)#123.',
     ];
@@ -541,8 +541,8 @@ run_test('python_to_js_filter', () => {
     // The only way to reach python_to_js_filter is indirectly, hence the call
     // to set_realm_filters.
     markdown.set_realm_filters([['/a(?im)a/g'], ['/a(?L)a/g']]);
-    var actual_value = marked.InlineLexer.rules.zulip.realm_filters;
-    var expected_value = [/\/aa\/g(?![\w])/gim, /\/aa\/g(?![\w])/g];
+    let actual_value = marked.InlineLexer.rules.zulip.realm_filters;
+    let expected_value = [/\/aa\/g(?![\w])/gim, /\/aa\/g(?![\w])/g];
     assert.deepEqual(actual_value, expected_value);
     // Test case with multiple replacements.
     markdown.set_realm_filters([['#cf(?P<contest>[0-9]+)(?P<problem>[A-Z][0-9A-Z]*)', 'http://google.com']]);
@@ -562,7 +562,7 @@ run_test('python_to_js_filter', () => {
 run_test('katex_throws_unexpected_exceptions', () => {
     katex.renderToString = function () { throw new Error('some-exception'); };
     blueslip.set_test_data('error', 'Error: some-exception');
-    var message = { raw_content: '$$a$$' };
+    const message = { raw_content: '$$a$$' };
     markdown.apply_markdown(message);
     assert.equal(blueslip.get_test_logs('error').length, 1);
     blueslip.clear_test_data();
diff --git a/frontend_tests/node_tests/settings_user_groups.js b/frontend_tests/node_tests/settings_user_groups.js
index 1d5687ea10..036138e79e 100644
--- a/frontend_tests/node_tests/settings_user_groups.js
+++ b/frontend_tests/node_tests/settings_user_groups.js
@@ -5,13 +5,13 @@ set_global('$', global.make_zjquery());
 set_global('i18n', global.stub_i18n);
 set_global('confirm_dialog', {});
 
-var noop = function () {};
+const noop = function () {};
 
-var pills = {
+const pills = {
     pill: {},
 };
 
-var create_item_handler;
+let create_item_handler;
 
 set_global('channel', {});
 set_global('blueslip', global.make_zblueslip());
@@ -83,31 +83,31 @@ run_test('can_edit', () => {
 
 });
 
-var user_group_selector = "#user-groups #1";
-var cancel_selector = "#user-groups #1 .save-status.btn-danger";
-var saved_selector = "#user-groups #1 .save-status.sea-green";
-var name_selector = "#user-groups #1 .name";
-var description_selector = "#user-groups #1 .description";
-var instructions_selector = "#user-groups #1 .save-instructions";
+const user_group_selector = "#user-groups #1";
+const cancel_selector = "#user-groups #1 .save-status.btn-danger";
+const saved_selector = "#user-groups #1 .save-status.sea-green";
+const name_selector = "#user-groups #1 .name";
+const description_selector = "#user-groups #1 .description";
+const instructions_selector = "#user-groups #1 .save-instructions";
 
 run_test('populate_user_groups', () => {
-    var realm_user_group = {
+    const realm_user_group = {
         id: 1,
         name: 'Mobile',
         description: 'All mobile people',
         members: Dict.from_array([2, 4]),
     };
-    var iago = {
+    const iago = {
         email: 'iago@zulip.com',
         user_id: 2,
         full_name: 'Iago',
     };
-    var alice = {
+    const alice = {
         email: 'alice@example.com',
         user_id: 31,
         full_name: 'Alice',
     };
-    var bob = {
+    const bob = {
         email: 'bob@example.com',
         user_id: 32,
         full_name: 'Bob',
@@ -121,8 +121,8 @@ run_test('populate_user_groups', () => {
         return [realm_user_group];
     };
 
-    var templates_render_called = false;
-    var fake_rendered_temp = $.create('fake_admin_user_group_list_template_rendered');
+    let templates_render_called = false;
+    const fake_rendered_temp = $.create('fake_admin_user_group_list_template_rendered');
     global.stub_templates(function (template, args) {
         assert.equal(template, 'admin_user_group_list');
         assert.equal(args.user_group.id, 1);
@@ -132,13 +132,13 @@ run_test('populate_user_groups', () => {
         return fake_rendered_temp;
     });
 
-    var user_groups_list_append_called = false;
+    let user_groups_list_append_called = false;
     $('#user-groups').append = function (rendered_temp) {
         assert.equal(rendered_temp, fake_rendered_temp);
         user_groups_list_append_called = true;
     };
 
-    var get_person_from_user_id_called = false;
+    let get_person_from_user_id_called = false;
     people.get_person_from_user_id = function (user_id) {
         if (user_id === iago.user_id) {
             return iago;
@@ -155,11 +155,11 @@ run_test('populate_user_groups', () => {
         return true;
     };
 
-    var all_pills = {};
+    const all_pills = {};
 
-    var pill_container_stub = $('.pill-container[data-group-pills="1"]');
+    const pill_container_stub = $('.pill-container[data-group-pills="1"]');
     pills.appendValidatedData = function (item) {
-        var id = item.user_id;
+        const id = item.user_id;
         assert.equal(all_pills[id], undefined);
         all_pills[id] = item;
     };
@@ -167,17 +167,17 @@ run_test('populate_user_groups', () => {
         return _.values(all_pills);
     };
 
-    var text_cleared;
+    let text_cleared;
     pills.clear_text = function () {
         text_cleared = true;
     };
 
-    var input_field_stub = $.create('fake-input-field');
+    const input_field_stub = $.create('fake-input-field');
     pill_container_stub.children = function () {
         return input_field_stub;
     };
 
-    var input_typeahead_called = false;
+    let input_typeahead_called = false;
     input_field_stub.typeahead = function (config) {
         assert.equal(config.items, 5);
         assert(config.fixed);
@@ -190,27 +190,27 @@ run_test('populate_user_groups', () => {
         assert.equal(typeof config.updater, 'function');
 
         (function test_highlighter() {
-            var fake_person = $.create('fake-person');
+            const fake_person = $.create('fake-person');
             typeahead_helper.render_person = function () {
                 return fake_person;
             };
             assert.equal(config.highlighter(), fake_person);
         }());
 
-        var fake_context = {
+        const fake_context = {
             query: 'ali',
         };
 
         (function test_source() {
-            var result = config.source.call(fake_context, iago);
-            var emails = _.pluck(result, 'email').sort();
+            const result = config.source.call(fake_context, iago);
+            const emails = _.pluck(result, 'email').sort();
             assert.deepEqual(emails, [alice.email, bob.email]);
         }());
 
         (function test_matcher() {
             /* Here the query doesn't begin with an '@' because typeahead is triggered
             by the '@' sign and thus removed in the query. */
-            var result = config.matcher.call(fake_context, iago);
+            let result = config.matcher.call(fake_context, iago);
             assert(!result);
 
             result = config.matcher.call(fake_context, alice);
@@ -218,7 +218,7 @@ run_test('populate_user_groups', () => {
         }());
 
         (function test_sorter() {
-            var sort_recipientbox_typeahead_called = false;
+            let sort_recipientbox_typeahead_called = false;
             typeahead_helper.sort_recipientbox_typeahead = function () {
                 sort_recipientbox_typeahead_called = true;
             };
@@ -232,9 +232,9 @@ run_test('populate_user_groups', () => {
                 return realm_user_group;
             };
 
-            var saved_fade_out_called = false;
-            var cancel_fade_to_called = false;
-            var instructions_fade_to_called = false;
+            let saved_fade_out_called = false;
+            let cancel_fade_to_called = false;
+            let instructions_fade_to_called = false;
             $(saved_selector).fadeOut = function () {
                 saved_fade_out_called = true;
             };
@@ -274,7 +274,7 @@ run_test('populate_user_groups', () => {
         input_typeahead_called = true;
     };
 
-    var get_by_email_called = false;
+    let get_by_email_called = false;
     people.get_by_email = function (user_email) {
         get_by_email_called = true;
         if (user_email === iago.email) {
@@ -293,14 +293,14 @@ run_test('populate_user_groups', () => {
 
     function test_create_item(handler) {
         (function test_rejection_path() {
-            var item = handler(iago.email, pills.items());
+            const item = handler(iago.email, pills.items());
             assert(get_by_email_called);
             assert.equal(item, undefined);
         }());
 
         (function test_success_path() {
             get_by_email_called = false;
-            var res = handler(bob.email, pills.items());
+            const res = handler(bob.email, pills.items());
             assert(get_by_email_called);
             assert.equal(typeof res, 'object');
             assert.equal(res.user_id, bob.user_id);
@@ -333,7 +333,7 @@ run_test('populate_user_groups', () => {
 });
 run_test('with_external_user', () => {
 
-    var realm_user_group = {
+    const realm_user_group = {
         id: 1,
         name: 'Mobile',
         description: 'All mobile people',
@@ -361,7 +361,7 @@ run_test('with_external_user', () => {
         return noop;
     };
 
-    var can_edit_called = 0;
+    let can_edit_called = 0;
     settings_user_groups.can_edit = function () {
         can_edit_called += 1;
         return false;
@@ -370,11 +370,11 @@ run_test('with_external_user', () => {
     // Reset zjquery to test stuff with user who cannot edit
     set_global('$', global.make_zjquery());
 
-    var user_group_find_called = 0;
-    var user_group_stub = $('div.user-group[id="1"]');
-    var name_field_stub = $.create('fake-name-field');
-    var description_field_stub = $.create('fake-description-field');
-    var input_stub = $.create('fake-input');
+    let user_group_find_called = 0;
+    const user_group_stub = $('div.user-group[id="1"]');
+    const name_field_stub = $.create('fake-name-field');
+    const description_field_stub = $.create('fake-description-field');
+    const input_stub = $.create('fake-input');
     user_group_stub.find = function (elem) {
         if (elem === '.name') {
             user_group_find_called += 1;
@@ -386,9 +386,9 @@ run_test('with_external_user', () => {
         }
     };
 
-    var pill_container_stub = $('.pill-container[data-group-pills="1"]');
-    var pill_stub = $.create('fake-pill');
-    var pill_container_find_called = 0;
+    const pill_container_stub = $('.pill-container[data-group-pills="1"]');
+    const pill_stub = $.create('fake-pill');
+    let pill_container_find_called = 0;
     pill_container_stub.find = function (elem) {
         if (elem === '.input') {
             pill_container_find_called += 1;
@@ -406,7 +406,7 @@ run_test('with_external_user', () => {
     };
 
     // Test the 'off' handlers on the pill-container
-    var turned_off = {};
+    const turned_off = {};
     pill_container_stub.off = function (event_name, sel) {
         if (sel === undefined) {
             sel = 'whole';
@@ -414,9 +414,9 @@ run_test('with_external_user', () => {
         turned_off[event_name + '/' + sel] = true;
     };
 
-    var pill_hover_called = false;
-    var callback;
-    var empty_fn;
+    let pill_hover_called = false;
+    let callback;
+    let empty_fn;
     pill_stub.hover = function (one, two) {
         callback = one;
         empty_fn = two;
@@ -425,9 +425,9 @@ run_test('with_external_user', () => {
         assert.equal(typeof two, 'function');
     };
 
-    var exit_button = $.create('fake-pill-exit');
+    const exit_button = $.create('fake-pill-exit');
     pill_stub.set_find_results('.exit', exit_button);
-    var exit_button_called = false;
+    let exit_button_called = false;
     exit_button.css = function (property, value) {
         exit_button_called = true;
         assert.equal(property, 'opacity');
@@ -447,32 +447,32 @@ run_test('with_external_user', () => {
 
     settings_user_groups.set_up();
 
-    var set_parents_result_called = 0;
-    var set_attributes_called = 0;
+    let set_parents_result_called = 0;
+    let set_attributes_called = 0;
 
     // Test different handlers with an external user
-    var delete_handler = $('#user-groups').get_on_handler('click', '.delete');
-    var fake_delete = $.create('fk-#user-groups.delete_btn');
+    const delete_handler = $('#user-groups').get_on_handler('click', '.delete');
+    const fake_delete = $.create('fk-#user-groups.delete_btn');
     fake_delete.set_parents_result('.user-group', $('.user-group'));
     set_parents_result_called += 1;
     $('.user-group').attr('id', '1');
     set_attributes_called += 1;
 
-    var name_update_handler = $(user_group_selector).get_on_handler("input", ".name");
+    const name_update_handler = $(user_group_selector).get_on_handler("input", ".name");
 
-    var des_update_handler = $(user_group_selector).get_on_handler("input", ".description");
+    const des_update_handler = $(user_group_selector).get_on_handler("input", ".description");
 
-    var member_change_handler = $(user_group_selector).get_on_handler("blur", ".input");
+    const member_change_handler = $(user_group_selector).get_on_handler("blur", ".input");
 
-    var name_change_handler = $(user_group_selector).get_on_handler("blur", ".name");
+    const name_change_handler = $(user_group_selector).get_on_handler("blur", ".name");
 
-    var des_change_handler = $(user_group_selector).get_on_handler("blur", ".description");
+    const des_change_handler = $(user_group_selector).get_on_handler("blur", ".description");
 
-    var event = {
+    const event = {
         stopPropagation: noop,
     };
-    var pill_click_called = false;
-    var pill_click_handler = pill_container_stub.get_on_handler('click');
+    let pill_click_called = false;
+    const pill_click_handler = pill_container_stub.get_on_handler('click');
     pill_click_called = true;
 
     assert(callback);
@@ -501,7 +501,7 @@ run_test('with_external_user', () => {
 
 run_test('reload', () => {
     $('#user-groups').html('Some text');
-    var populate_user_groups_called = false;
+    let populate_user_groups_called = false;
     settings_user_groups.populate_user_groups = function () {
         populate_user_groups_called = true;
     };
@@ -512,7 +512,7 @@ run_test('reload', () => {
 
 run_test('reset', () => {
     settings_user_groups.reset();
-    var result = settings_user_groups.reload();
+    const result = settings_user_groups.reload();
     assert.equal(result, undefined);
 });
 
@@ -523,13 +523,13 @@ run_test('on_events', () => {
     };
 
     (function test_admin_user_group_form_submit_triggered() {
-        var handler = $('.organization form.admin-user-group-form').get_on_handler("submit");
-        var event = {
+        const handler = $('.organization form.admin-user-group-form').get_on_handler("submit");
+        const event = {
             stopPropagation: noop,
             preventDefault: noop,
         };
-        var fake_this = $.create('fake-form.admin-user-group-form');
-        var fake_object_array = [{
+        const fake_this = $.create('fake-form.admin-user-group-form');
+        const fake_object_array = [{
             name: 'fake-name',
             value: '',
         }, {
@@ -540,7 +540,7 @@ run_test('on_events', () => {
             return fake_object_array;
         };
         channel.post = function (opts) {
-            var data = {
+            const data = {
                 members: '[null]',
             };
             data[fake_object_array[1].name] = fake_object_array[1].value;
@@ -564,14 +564,14 @@ run_test('on_events', () => {
             (function test_post_error() {
                 $('#admin-user-group-status').show();
                 ui_report.error = function (error_msg, error_obj, ele) {
-                    var xhr = {
+                    const xhr = {
                         responseText: '{"msg":"fake-msg"}',
                     };
                     assert.equal(error_msg, 'translated: Failed');
                     assert.deepEqual(error_obj, xhr);
                     assert.equal(ele, $('#admin-user-group-status'));
                 };
-                var xhr = {
+                const xhr = {
                     responseText: '{"msg":"fake-msg", "attrib":"val"}',
                 };
                 opts.error(xhr);
@@ -584,16 +584,16 @@ run_test('on_events', () => {
     }());
 
     (function test_user_groups_delete_click_triggered() {
-        var handler = $('#user-groups').get_on_handler("click", ".delete");
-        var fake_this = $.create('fake-#user-groups.delete_btn');
+        const handler = $('#user-groups').get_on_handler("click", ".delete");
+        const fake_this = $.create('fake-#user-groups.delete_btn');
         fake_this.set_parents_result('.user-group', $('.user-group'));
         $('.user-group').attr('id', '1');
 
         channel.del = function (opts) {
-            var data = {
+            const data = {
                 id: 1,
             };
-            var settings_user_groups_reload_called = false;
+            let settings_user_groups_reload_called = false;
             assert.equal(opts.url, "/json/user_groups/1");
             assert.deepEqual(opts.data, data);
 
@@ -616,9 +616,9 @@ run_test('on_events', () => {
     }());
 
     (function test_user_groups_keypress_enter_triggered() {
-        var handler = $('#user-groups').get_on_handler("keypress", ".user-group h4 > span");
-        var default_action_for_enter_stopped = false;
-        var event = {
+        const handler = $('#user-groups').get_on_handler("keypress", ".user-group h4 > span");
+        let default_action_for_enter_stopped = false;
+        const event = {
             which: 13,
             preventDefault: function () {
                 default_action_for_enter_stopped = true;
@@ -629,22 +629,22 @@ run_test('on_events', () => {
     }());
 
     (function test_do_not_blur() {
-        var blur_event_classes = [".name", ".description", ".input"];
-        var api_endpoint_called = false;
+        const blur_event_classes = [".name", ".description", ".input"];
+        let api_endpoint_called = false;
         channel.post = function () {
             api_endpoint_called = true;
         };
         channel.patch = noop;
-        var fake_this = $.create('fake-#user-groups_do_not_blur');
-        var event = {
+        const fake_this = $.create('fake-#user-groups_do_not_blur');
+        const event = {
             relatedTarget: fake_this,
         };
 
         // Any of the blur_exceptions trigger blur event.
         _.each(blur_event_classes, function (class_name) {
-            var handler = $(user_group_selector).get_on_handler("blur", class_name);
-            var blur_exceptions = _.without([".pill-container", ".name", ".description", ".input", ".delete"],
-                                            class_name);
+            const handler = $(user_group_selector).get_on_handler("blur", class_name);
+            const blur_exceptions = _.without([".pill-container", ".name", ".description", ".input", ".delete"],
+                                              class_name);
             _.each(blur_exceptions, function (blur_exception) {
                 api_endpoint_called = false;
                 fake_this.closest = function (class_name) {
@@ -668,7 +668,7 @@ run_test('on_events', () => {
             assert(!api_endpoint_called);
 
             // Cancel button triggers blur event.
-            var settings_user_groups_reload_called = false;
+            let settings_user_groups_reload_called = false;
             settings_user_groups.reload = function () {
                 settings_user_groups_reload_called = true;
             };
@@ -687,14 +687,14 @@ run_test('on_events', () => {
     }());
 
     (function test_update_cancel_button() {
-        var handler_name = $(user_group_selector).get_on_handler("input", ".name");
-        var handler_desc = $(user_group_selector).get_on_handler("input", ".description");
-        var sib_des = $(description_selector);
-        var sib_name = $(name_selector);
+        const handler_name = $(user_group_selector).get_on_handler("input", ".name");
+        const handler_desc = $(user_group_selector).get_on_handler("input", ".description");
+        const sib_des = $(description_selector);
+        const sib_name = $(name_selector);
         sib_name.text(i18n.t('mobile'));
         sib_des.text(i18n.t('All mobile members'));
 
-        var group_data = {
+        const group_data = {
             name: 'translated: mobile',
             description: 'translated: All mobile members',
             members: Dict.from_array([2, 31])};
@@ -702,8 +702,8 @@ run_test('on_events', () => {
             return group_data;
         };
 
-        var cancel_fade_out_called = false;
-        var instructions_fade_out_called = false;
+        let cancel_fade_out_called = false;
+        let instructions_fade_out_called = false;
         $(cancel_selector).show();
         $(cancel_selector).fadeOut = function () {
             cancel_fade_out_called = true;
@@ -713,7 +713,7 @@ run_test('on_events', () => {
         };
 
         // Cancel button removed if user group if user group has no changes.
-        var fake_this = $.create('fake-#update_cancel_button');
+        const fake_this = $.create('fake-#update_cancel_button');
         handler_name.call(fake_this);
         assert(cancel_fade_out_called);
         assert(instructions_fade_out_called);
@@ -735,21 +735,21 @@ run_test('on_events', () => {
     }());
 
     (function test_user_groups_save_group_changes_triggered() {
-        var handler_name = $(user_group_selector).get_on_handler("blur", ".name");
-        var handler_desc = $(user_group_selector).get_on_handler("blur", ".description");
-        var sib_des = $(description_selector);
-        var sib_name = $(name_selector);
+        const handler_name = $(user_group_selector).get_on_handler("blur", ".name");
+        const handler_desc = $(user_group_selector).get_on_handler("blur", ".description");
+        const sib_des = $(description_selector);
+        const sib_name = $(name_selector);
         sib_name.text(i18n.t('mobile'));
         sib_des.text(i18n.t('All mobile members'));
 
-        var group_data = {members: Dict.from_array([2, 31])};
+        const group_data = {members: Dict.from_array([2, 31])};
         user_groups.get_user_group_from_id = function () {
             return group_data;
         };
-        var api_endpoint_called = false;
-        var cancel_fade_out_called = false;
-        var saved_fade_to_called = false;
-        var instructions_fade_out_called = false;
+        let api_endpoint_called = false;
+        let cancel_fade_out_called = false;
+        let saved_fade_to_called = false;
+        let instructions_fade_out_called = false;
         $(instructions_selector).fadeOut = function () {
             instructions_fade_out_called = true;
         };
@@ -785,17 +785,17 @@ run_test('on_events', () => {
                 assert(saved_fade_to_called);
             }());
             (function test_post_error() {
-                var user_group_error = $(user_group_selector + ' .user-group-status');
+                const user_group_error = $(user_group_selector + ' .user-group-status');
                 user_group_error.show();
                 ui_report.error = function (error_msg, error_obj, ele) {
-                    var xhr = {
+                    const xhr = {
                         responseText: '{"msg":"fake-msg"}',
                     };
                     assert.equal(error_msg, 'translated: Failed');
                     assert.deepEqual(error_obj, xhr);
                     assert.equal(ele, user_group_error);
                 };
-                var xhr = {
+                const xhr = {
                     responseText: '{"msg":"fake-msg", "attrib":"val"}',
                 };
                 opts.error(xhr);
@@ -804,12 +804,12 @@ run_test('on_events', () => {
             }());
         };
 
-        var fake_this = $.create('fake-#user-groups_blur_name');
+        const fake_this = $.create('fake-#user-groups_blur_name');
         fake_this.closest = function () {
             return [];
         };
         fake_this.set_parents_result(user_group_selector, $(user_group_selector));
-        var event = {
+        const event = {
             relatedTarget: fake_this,
         };
 
@@ -831,8 +831,8 @@ run_test('on_events', () => {
     }());
 
     (function test_user_groups_save_member_changes_triggered() {
-        var handler = $(user_group_selector).get_on_handler("blur", ".input");
-        var realm_user_group = {
+        const handler = $(user_group_selector).get_on_handler("blur", ".input");
+        const realm_user_group = {
             id: 1,
             name: 'Mobile',
             description: 'All mobile people',
@@ -844,9 +844,9 @@ run_test('on_events', () => {
             return realm_user_group;
         };
 
-        var cancel_fade_out_called = false;
-        var saved_fade_to_called = false;
-        var instructions_fade_out_called = false;
+        let cancel_fade_out_called = false;
+        let saved_fade_to_called = false;
+        let instructions_fade_out_called = false;
         $(instructions_selector).fadeOut = function () {
             instructions_fade_out_called = true;
         };
@@ -861,7 +861,7 @@ run_test('on_events', () => {
             return $(saved_selector);
         };
 
-        var api_endpoint_called = false;
+        let api_endpoint_called = false;
         channel.post = function (opts) {
             assert.equal(opts.url, "/json/user_groups/1/members");
             assert.equal(opts.data.add, '[31]');
@@ -876,12 +876,12 @@ run_test('on_events', () => {
             }());
         };
 
-        var fake_this = $.create('fake-#user-groups_blur_input');
+        const fake_this = $.create('fake-#user-groups_blur_input');
         fake_this.set_parents_result(user_group_selector, $(user_group_selector));
         fake_this.closest = function () {
             return [];
         };
-        var event = {
+        const event = {
             relatedTarget: fake_this,
         };
 
diff --git a/frontend_tests/node_tests/templates.js b/frontend_tests/node_tests/templates.js
index f31c726cab..ed66880f76 100644
--- a/frontend_tests/node_tests/templates.js
+++ b/frontend_tests/node_tests/templates.js
@@ -1590,7 +1590,7 @@ run_test('user_presence_rows', () => {
 });
 
 run_test('buddy_list_tooltip_content', () => {
-    var args = {
+    const args = {
         status_text: 'out to lunch',
         last_seen: 'Active now',
         is_away: false,
@@ -1598,8 +1598,8 @@ run_test('buddy_list_tooltip_content', () => {
         online_now: true,
     };
 
-    var html = render('buddy_list_tooltip_content', args);
-    var tooltip_content = $(html).find(".tooltip_inner_content");
+    const html = render('buddy_list_tooltip_content', args);
+    const tooltip_content = $(html).find(".tooltip_inner_content");
     assert.equal(tooltip_content.text().trim(), 'Iagoout to lunchActive now');
 });
 
diff --git a/static/js/buddy_data.js b/static/js/buddy_data.js
index 5b6f11f81c..4df9e633c1 100644
--- a/static/js/buddy_data.js
+++ b/static/js/buddy_data.js
@@ -9,7 +9,7 @@
 
 exports.max_size_before_shrinking = 600;
 
-var fade_config = {
+const fade_config = {
     get_user_id: function (item) {
         return item.user_id;
     },
@@ -22,7 +22,7 @@ var fade_config = {
 };
 
 exports.get_user_circle_class = function (user_id) {
-    var status = exports.buddy_status(user_id);
+    const status = exports.buddy_status(user_id);
 
     switch (status) {
     case 'active':
@@ -38,7 +38,7 @@ exports.get_user_circle_class = function (user_id) {
 };
 
 exports.status_description = function (user_id) {
-    var status = exports.buddy_status(user_id);
+    const status = exports.buddy_status(user_id);
 
     switch (status) {
     case 'active':
@@ -59,7 +59,7 @@ exports.level = function (user_id) {
         return 0;
     }
 
-    var status = exports.buddy_status(user_id);
+    const status = exports.buddy_status(user_id);
 
     switch (status) {
     case 'active':
@@ -87,19 +87,19 @@ exports.buddy_status = function (user_id) {
 };
 
 exports.compare_function = function (a, b) {
-    var level_a = exports.level(a);
-    var level_b = exports.level(b);
-    var diff = level_a - level_b;
+    const level_a = exports.level(a);
+    const level_b = exports.level(b);
+    const diff = level_a - level_b;
     if (diff !== 0) {
         return diff;
     }
 
     // Sort equivalent PM names alphabetically
-    var person_a = people.get_person_from_user_id(a);
-    var person_b = people.get_person_from_user_id(b);
+    const person_a = people.get_person_from_user_id(a);
+    const person_b = people.get_person_from_user_id(b);
 
-    var full_name_a = person_a ? person_a.full_name : '';
-    var full_name_b = person_b ? person_b.full_name : '';
+    const full_name_a = person_a ? person_a.full_name : '';
+    const full_name_b = person_b ? person_b.full_name : '';
 
     return util.strcmp(full_name_a, full_name_b);
 };
@@ -117,16 +117,16 @@ function filter_user_ids(filter_text, user_ids) {
 
     user_ids = _.reject(user_ids, people.is_my_user_id);
 
-    var search_terms = filter_text.toLowerCase().split(/[|,]+/);
+    let search_terms = filter_text.toLowerCase().split(/[|,]+/);
     search_terms = _.map(search_terms, function (s) {
         return s.trim();
     });
 
-    var persons = _.map(user_ids, function (user_id) {
+    const persons = _.map(user_ids, function (user_id) {
         return people.get_person_from_user_id(user_id);
     });
 
-    var user_id_dict = people.filter_people_by_search_terms(persons, search_terms);
+    const user_id_dict = people.filter_people_by_search_terms(persons, search_terms);
     return user_id_dict.keys();
 }
 
@@ -156,7 +156,7 @@ exports.my_user_status = function (user_id) {
 };
 
 exports.user_last_seen_time_status = function (user_id) {
-    var status = presence.get_status(user_id);
+    const status = presence.get_status(user_id);
     if (status === "active") {
         return i18n.t("Active now");
     }
@@ -172,7 +172,7 @@ exports.user_last_seen_time_status = function (user_id) {
     // may have queries on presence that go back only N weeks).
     //
     // We give the somewhat vague status of "Unknown" for these users.
-    var last_active_date = presence.last_active_date(user_id);
+    const last_active_date = presence.last_active_date(user_id);
     if (last_active_date === undefined) {
         return i18n.t("More than 2 weeks ago");
     }
@@ -180,10 +180,10 @@ exports.user_last_seen_time_status = function (user_id) {
 };
 
 exports.info_for = function (user_id) {
-    var user_circle_class = exports.get_user_circle_class(user_id);
-    var person = people.get_person_from_user_id(user_id);
-    var my_user_status = exports.my_user_status(user_id);
-    var user_circle_status = exports.status_description(user_id);
+    const user_circle_class = exports.get_user_circle_class(user_id);
+    const person = people.get_person_from_user_id(user_id);
+    const my_user_status = exports.my_user_status(user_id);
+    const user_circle_status = exports.status_description(user_id);
 
     return {
         href: hash_util.pm_with_uri(person.email),
@@ -208,9 +208,9 @@ exports.get_title_data = function (user_ids_string, is_group) {
     }
 
     // Since it's not a group, user_ids_string is a single user ID.
-    var user_id = user_ids_string;
-    var person = people.get_person_from_user_id(user_id);
-    var bot_owner_exists = false;
+    const user_id = user_ids_string;
+    const person = people.get_person_from_user_id(user_id);
+    let bot_owner_exists = false;
 
     if (person.is_bot) {
         if (person.bot_owner_id !== null) {
@@ -231,9 +231,9 @@ exports.get_title_data = function (user_ids_string, is_group) {
 
     // For buddy list and individual PMS.  Since is_group=False, it's
     // a single, human, user.
-    var active_status = presence.get_status(user_id);
-    var last_seen = exports.user_last_seen_time_status(user_id);
-    var online_now = active_status === 'active';
+    const active_status = presence.get_status(user_id);
+    const last_seen = exports.user_last_seen_time_status(user_id);
+    const online_now = active_status === 'active';
 
     return {
         is_group: '',
@@ -247,7 +247,7 @@ exports.get_title_data = function (user_ids_string, is_group) {
 };
 
 exports.get_item = function (user_id) {
-    var info = exports.info_for(user_id);
+    const info = exports.info_for(user_id);
     compose_fade.update_user_info([info], fade_config);
     return info;
 };
@@ -278,7 +278,7 @@ function maybe_shrink_list(user_ids, filter_text) {
 }
 
 exports.get_filtered_and_sorted_user_ids = function (filter_text) {
-    var user_ids;
+    let user_ids;
 
     if (filter_text) {
         // If there's a filter, select from all users, not just those
@@ -292,7 +292,7 @@ exports.get_filtered_and_sorted_user_ids = function (filter_text) {
     }
 
     user_ids = _.filter(user_ids, function (user_id) {
-        var person = people.get_person_from_user_id(user_id);
+        const person = people.get_person_from_user_id(user_id);
 
         if (person) {
             // if the user is bot, do not show in presence data.
@@ -310,7 +310,7 @@ exports.get_filtered_and_sorted_user_ids = function (filter_text) {
 };
 
 exports.get_items_for_users = function (user_ids) {
-    var user_info = _.map(user_ids, exports.info_for).filter(function (person) {
+    const user_info = _.map(user_ids, exports.info_for).filter(function (person) {
         // filtered bots and yourself are set to "undefined" in the `info_for`
         // function.
         return typeof person !== "undefined";
@@ -322,9 +322,9 @@ exports.get_items_for_users = function (user_ids) {
 };
 
 exports.huddle_fraction_present = function (huddle) {
-    var user_ids = huddle.split(',');
+    const user_ids = huddle.split(',');
 
-    var num_present = 0;
+    let num_present = 0;
     _.each(user_ids, function (user_id) {
         if (presence.is_active(user_id)) {
             num_present += 1;
diff --git a/static/js/click_handlers.js b/static/js/click_handlers.js
index d7317531f0..afd4d5fcea 100644
--- a/static/js/click_handlers.js
+++ b/static/js/click_handlers.js
@@ -1,15 +1,15 @@
 // You won't find every click handler here, but it's a good place to start!
 
-var render_buddy_list_tooltip = require('../templates/buddy_list_tooltip.hbs');
-var render_buddy_list_tooltip_content = require('../templates/buddy_list_tooltip_content.hbs');
+const render_buddy_list_tooltip = require('../templates/buddy_list_tooltip.hbs');
+const render_buddy_list_tooltip_content = require('../templates/buddy_list_tooltip_content.hbs');
 
 exports.initialize = function () {
 
     // MOUSE MOVING VS DRAGGING FOR SELECTION DATA TRACKING
 
-    var drag = (function () {
-        var start;
-        var time;
+    const drag = (function () {
+        let start;
+        let time;
 
         return {
             start: function (e) {
@@ -18,9 +18,9 @@ exports.initialize = function () {
             },
 
             end: function (e) {
-                var end = { x: e.offsetX, y: e.offsetY };
+                const end = { x: e.offsetX, y: e.offsetY };
 
-                var dist;
+                let dist;
                 if (start) {
                     // get the linear difference between two coordinates on the screen.
                     dist = Math.sqrt(Math.pow(end.x - start.x, 2) + Math.pow(end.y - start.y, 2));
@@ -60,8 +60,8 @@ exports.initialize = function () {
     }
 
     function initialize_long_tap() {
-        var MS_DELAY = 750;
-        var meta = {
+        const MS_DELAY = 750;
+        const meta = {
             touchdown: false,
             current_target: undefined,
         };
@@ -69,7 +69,7 @@ exports.initialize = function () {
         $("#main_div").on("touchstart", ".messagebox", function () {
             meta.touchdown = true;
             meta.invalid = false;
-            var id = rows.id($(this).closest(".message_row"));
+            const id = rows.id($(this).closest(".message_row"));
             meta.current_target = id;
             if (!id) {
                 return;
@@ -111,7 +111,7 @@ exports.initialize = function () {
         initialize_long_tap();
     }
 
-    var select_message_function = function (e) {
+    const select_message_function = function (e) {
         if (is_clickable_message_element($(e.target))) {
             // If this click came from a hyperlink, don't trigger the
             // reply action.  The simple way of doing this is simply
@@ -139,8 +139,8 @@ exports.initialize = function () {
         // older browsers, we may be able to use the window.selection
         // API instead.
         if (drag.val < 5 && drag.time < 150 || drag.val < 2) {
-            var row = $(this).closest(".message_row");
-            var id = rows.id(row);
+            const row = $(this).closest(".message_row");
+            const id = rows.id(row);
 
             if (message_edit.is_editing(id)) {
                 // Clicks on a message being edited shouldn't trigger a reply.
@@ -162,7 +162,7 @@ exports.initialize = function () {
     } else {
         $("#main_div").on("longtap", ".messagebox", function (e) {
             // find the correct selection API for the browser.
-            var sel = window.getSelection ? window.getSelection() : document.selection;
+            const sel = window.getSelection ? window.getSelection() : document.selection;
             // if one matches, remove the current selections.
             // after a longtap that is valid, there should be no text selected.
             if (sel) {
@@ -181,15 +181,15 @@ exports.initialize = function () {
         e.stopPropagation();
         popovers.hide_all();
 
-        var message_id = rows.id($(this).closest(".message_row"));
-        var message = message_store.get(message_id);
+        const message_id = rows.id($(this).closest(".message_row"));
+        const message = message_store.get(message_id);
         message_flags.toggle_starred_and_update_server(message);
     });
 
     $("#main_div").on("click", ".message_reaction", function (e) {
         e.stopPropagation();
-        var local_id = $(this).attr('data-reaction-id');
-        var message_id = rows.get_message_id(this);
+        const local_id = $(this).attr('data-reaction-id');
+        const message_id = rows.get_message_id(this);
         reactions.process_reaction_click(message_id, local_id);
         $(".tooltip").remove();
     });
@@ -208,10 +208,10 @@ exports.initialize = function () {
 
     $('body').on('click', '.message_edit_notice', function (e) {
         popovers.hide_all();
-        var message_id = rows.id($(e.currentTarget).closest(".message_row"));
-        var row = current_msg_list.get_row(message_id);
-        var message = current_msg_list.get(rows.id(row));
-        var message_history_cancel_btn = $('#message-history-cancel');
+        const message_id = rows.id($(e.currentTarget).closest(".message_row"));
+        const row = current_msg_list.get_row(message_id);
+        const message = current_msg_list.get(rows.id(row));
+        const message_history_cancel_btn = $('#message-history-cancel');
 
         if (page_params.realm_allow_edit_history) {
             message_edit.show_history(message);
@@ -225,10 +225,10 @@ exports.initialize = function () {
 
     $('#main_div').on('mouseenter', '.message_reaction', function (e) {
         e.stopPropagation();
-        var elem = $(e.currentTarget);
-        var local_id = elem.attr('data-reaction-id');
-        var message_id = rows.get_message_id(e.currentTarget);
-        var title = reactions.get_reaction_title_data(message_id, local_id);
+        const elem = $(e.currentTarget);
+        const local_id = elem.attr('data-reaction-id');
+        const message_id = rows.get_message_id(e.currentTarget);
+        const title = reactions.get_reaction_title_data(message_id, local_id);
 
         elem.tooltip({
             title: title,
@@ -258,7 +258,7 @@ exports.initialize = function () {
         e.preventDefault();
         // Note that we may have an href here, but we trust the stream id more,
         // so we re-encode the hash.
-        var stream_id = $(this).attr('data-stream-id');
+        const stream_id = $(this).attr('data-stream-id');
         if (stream_id) {
             hashchange.go_to_location(hash_util.by_stream_uri(stream_id));
             return;
@@ -270,7 +270,7 @@ exports.initialize = function () {
 
     $(".user-status-value").on("click", function (e) {
         e.stopPropagation();
-        var user_status_value = $(e.currentTarget).attr("data-user-status-value");
+        const user_status_value = $(e.currentTarget).attr("data-user-status-value");
         $("input.user_status").val(user_status_value);
         user_status_ui.toggle_clear_message_button();
         user_status_ui.update_button();
@@ -279,7 +279,7 @@ exports.initialize = function () {
     // NOTIFICATION CLICK
 
     $('body').on('click', '.notification', function () {
-        var payload = $(this).data("narrow");
+        const payload = $(this).data("narrow");
         ui_util.change_tab_to('#home');
         narrow.activate(payload.raw_operators, payload.opts_notif);
     });
@@ -287,51 +287,51 @@ exports.initialize = function () {
     // MESSAGE EDITING
 
     $('body').on('click', '.edit_content_button', function (e) {
-        var row = current_msg_list.get_row(rows.id($(this).closest(".message_row")));
+        const row = current_msg_list.get_row(rows.id($(this).closest(".message_row")));
         current_msg_list.select_id(rows.id(row));
         message_edit.start(row);
         e.stopPropagation();
         popovers.hide_all();
     });
     $('body').on('click', '.always_visible_topic_edit,.on_hover_topic_edit', function (e) {
-        var recipient_row = $(this).closest(".recipient_row");
+        const recipient_row = $(this).closest(".recipient_row");
         message_edit.start_topic_edit(recipient_row);
         e.stopPropagation();
         popovers.hide_all();
     });
     $("body").on("click", ".topic_edit_save", function (e) {
-        var recipient_row = $(this).closest(".recipient_row");
+        const recipient_row = $(this).closest(".recipient_row");
         message_edit.show_topic_edit_spinner(recipient_row);
         message_edit.save(recipient_row, true);
         e.stopPropagation();
         popovers.hide_all();
     });
     $("body").on("click", ".topic_edit_cancel", function (e) {
-        var recipient_row = $(this).closest(".recipient_row");
+        const recipient_row = $(this).closest(".recipient_row");
         current_msg_list.hide_edit_topic(recipient_row);
         e.stopPropagation();
         popovers.hide_all();
     });
     $("body").on("click", ".message_edit_save", function (e) {
-        var row = $(this).closest(".message_row");
+        const row = $(this).closest(".message_row");
         message_edit.save(row, false);
         e.stopPropagation();
         popovers.hide_all();
     });
     $("body").on("click", ".message_edit_cancel", function (e) {
-        var row = $(this).closest(".message_row");
+        const row = $(this).closest(".message_row");
         message_edit.end(row);
         e.stopPropagation();
         popovers.hide_all();
     });
     $("body").on("click", ".message_edit_close", function (e) {
-        var row = $(this).closest(".message_row");
+        const row = $(this).closest(".message_row");
         message_edit.end(row);
         e.stopPropagation();
         popovers.hide_all();
     });
     $("body").on("click", ".copy_message", function (e) {
-        var row = $(this).closest(".message_row");
+        const row = $(this).closest(".message_row");
         message_edit.end(row);
         row.find(".alert-msg").text(i18n.t("Copied!"));
         row.find(".alert-msg").css("display", "block");
@@ -345,26 +345,26 @@ exports.initialize = function () {
         }
     });
     $('#message_edit_form .send-status-close').click(function () {
-        var row_id = rows.id($(this).closest(".message_row"));
-        var send_status = $('#message-edit-send-status-' + row_id);
+        const row_id = rows.id($(this).closest(".message_row"));
+        const send_status = $('#message-edit-send-status-' + row_id);
         $(send_status).stop(true).fadeOut(200);
     });
     $("body").on("click", "#message_edit_form [id^='attach_files_']", function (e) {
         e.preventDefault();
 
-        var row_id = rows.id($(this).closest(".message_row"));
+        const row_id = rows.id($(this).closest(".message_row"));
         $("#message_edit_file_input_" + row_id).trigger("click");
     });
 
     $("body").on("click", "#message_edit_form [id^='markdown_preview_']", function (e) {
         e.preventDefault();
 
-        var row_id = rows.id($(this).closest(".message_row"));
+        const row_id = rows.id($(this).closest(".message_row"));
         function $_(selector) {
             return $(selector + "_" + row_id);
         }
 
-        var content = $_("#message_edit_content").val();
+        const content = $_("#message_edit_content").val();
         $_("#message_edit_content").hide();
         $_("#markdown_preview").hide();
         $_("#undo_markdown_preview").show();
@@ -376,7 +376,7 @@ exports.initialize = function () {
     $("body").on("click", "#message_edit_form [id^='undo_markdown_preview_']", function (e) {
         e.preventDefault();
 
-        var row_id = rows.id($(this).closest(".message_row"));
+        const row_id = rows.id($(this).closest(".message_row"));
         function $_(selector) {
             return $(selector + "_" + row_id);
         }
@@ -392,19 +392,19 @@ exports.initialize = function () {
 
     $('body').on('click', '.on_hover_topic_mute', function (e) {
         e.stopPropagation();
-        var stream_id = $(e.currentTarget).attr('data-stream-id');
-        var topic = $(e.currentTarget).attr('data-topic-name');
+        const stream_id = $(e.currentTarget).attr('data-stream-id');
+        const topic = $(e.currentTarget).attr('data-topic-name');
         muting_ui.mute(stream_id, topic);
     });
 
     // RECIPIENT BARS
 
     function get_row_id_for_narrowing(narrow_link_elem) {
-        var group = rows.get_closest_group(narrow_link_elem);
-        var msg_id = rows.id_for_recipient_row(group);
+        const group = rows.get_closest_group(narrow_link_elem);
+        const msg_id = rows.id_for_recipient_row(group);
 
-        var nearest = current_msg_list.get(msg_id);
-        var selected = current_msg_list.selected_message();
+        const nearest = current_msg_list.get(msg_id);
+        const selected = current_msg_list.selected_message();
         if (util.same_recipient(nearest, selected)) {
             return selected.id;
         }
@@ -416,7 +416,7 @@ exports.initialize = function () {
             return;
         }
         e.preventDefault();
-        var row_id = get_row_id_for_narrowing(this);
+        const row_id = get_row_id_for_narrowing(this);
         narrow.by_recipient(row_id, {trigger: 'message header'});
     });
 
@@ -425,7 +425,7 @@ exports.initialize = function () {
             return;
         }
         e.preventDefault();
-        var row_id = get_row_id_for_narrowing(this);
+        const row_id = get_row_id_for_narrowing(this);
         narrow.by_topic(row_id, {trigger: 'message header'});
     });
 
@@ -435,7 +435,7 @@ exports.initialize = function () {
         e.preventDefault();
         e.stopPropagation();
 
-        var sidebarHidden = !$(".app-main .column-right").hasClass("expanded");
+        const sidebarHidden = !$(".app-main .column-right").hasClass("expanded");
         popovers.hide_all();
         if (sidebarHidden) {
             popovers.show_userlist_sidebar();
@@ -446,7 +446,7 @@ exports.initialize = function () {
         e.preventDefault();
         e.stopPropagation();
 
-        var sidebarHidden = !$(".app-main .column-left").hasClass("expanded");
+        const sidebarHidden = !$(".app-main .column-left").hasClass("expanded");
         popovers.hide_all();
         if (sidebarHidden) {
             stream_popover.show_streamlist_sidebar();
@@ -454,7 +454,7 @@ exports.initialize = function () {
     });
 
     $('#user_presences').expectOne().on('click', '.selectable_sidebar_block', function (e) {
-        var li = $(e.target).parents('li');
+        const li = $(e.target).parents('li');
 
         activity.narrow_for_user({li: li});
 
@@ -465,8 +465,8 @@ exports.initialize = function () {
     });
 
     $('#group-pms').expectOne().on('click', '.selectable_sidebar_block', function (e) {
-        var user_ids_string = $(e.target).parents('li').attr('data-user-ids');
-        var emails = people.user_ids_string_to_emails_string(user_ids_string);
+        const user_ids_string = $(e.target).parents('li').attr('data-user-ids');
+        const emails = people.user_ids_string_to_emails_string(user_ids_string);
         narrow.by('pm-with', emails, {trigger: 'sidebar'});
         e.preventDefault();
         e.stopPropagation();
@@ -498,15 +498,15 @@ exports.initialize = function () {
     // BUDDY LIST TOOLTIPS
     $('#user_presences').on('mouseenter', '.user-presence-link, .user_sidebar_entry .user_circle, .user_sidebar_entry .selectable_sidebar_block', function (e) {
         e.stopPropagation();
-        var elem = $(e.currentTarget).closest(".user_sidebar_entry").find(".user-presence-link");
-        var user_id = elem.attr('data-user-id');
-        var title_data = buddy_data.get_title_data(user_id, false);
+        const elem = $(e.currentTarget).closest(".user_sidebar_entry").find(".user-presence-link");
+        const user_id = elem.attr('data-user-id');
+        const title_data = buddy_data.get_title_data(user_id, false);
         do_render_buddy_list_tooltip(elem, title_data);
     });
 
     $('#user_presences').on('mouseleave click', '.user-presence-link, .user_sidebar_entry .user_circle, .user_sidebar_entry .selectable_sidebar_block', function (e) {
         e.stopPropagation();
-        var elem = $(e.currentTarget).closest(".user_sidebar_entry").find(".user-presence-link");
+        const elem = $(e.currentTarget).closest(".user_sidebar_entry").find(".user-presence-link");
         $(elem).tooltip('destroy');
     });
 
@@ -514,12 +514,12 @@ exports.initialize = function () {
     $("body").on('mouseenter', '#pm_user_status, #group_pms_right_sidebar', function (e) {
         $(".tooltip").remove();
         e.stopPropagation();
-        var elem = $(e.currentTarget);
-        var user_ids_string = elem.attr('data-user-ids-string');
+        const elem = $(e.currentTarget);
+        const user_ids_string = elem.attr('data-user-ids-string');
         // This converts from 'true' in the DOM to true.
-        var is_group = JSON.parse(elem.attr('data-is-group'));
+        const is_group = JSON.parse(elem.attr('data-is-group'));
 
-        var title_data = buddy_data.get_title_data(user_ids_string, is_group);
+        const title_data = buddy_data.get_title_data(user_ids_string, is_group);
         do_render_buddy_list_tooltip(elem, title_data);
     });
 
@@ -553,7 +553,7 @@ exports.initialize = function () {
     // MISC
 
     (function () {
-        var sel = ["#group-pm-list", "#stream_filters", "#global_filters", "#user_presences"].join(", ");
+        const sel = ["#group-pm-list", "#stream_filters", "#global_filters", "#user_presences"].join(", ");
 
         $(sel).on("click", "a", function () {
             this.blur();
@@ -575,7 +575,7 @@ exports.initialize = function () {
 
     // this will hide the alerts that you click "x" on.
     $("body").on("click", ".alert-box > div .exit", function () {
-        var $alert = $(this).closest(".alert-box > div");
+        const $alert = $(this).closest(".alert-box > div");
         $alert.addClass("fade-out");
         setTimeout(function () {
             $alert.removeClass("fade-out show");
@@ -634,7 +634,7 @@ exports.initialize = function () {
     });
 
     $("body").on("click", "[data-overlay-trigger]", function () {
-        var target = $(this).attr("data-overlay-trigger");
+        const target = $(this).attr("data-overlay-trigger");
         info_overlay.show(target);
     });
 
@@ -704,7 +704,7 @@ exports.initialize = function () {
 
     $('body').on('click', '.webathena_login', function (e) {
         $("#zephyr-mirror-error").removeClass("show");
-        var principal = ["zephyr", "zephyr"];
+        const principal = ["zephyr", "zephyr"];
         WinChan.open({
             url: "https://webathena.mit.edu/#!request_ticket_v1",
             relay_url: "https://webathena.mit.edu/relay.html",
@@ -745,7 +745,7 @@ exports.initialize = function () {
     });
 
     (function () {
-        var map = {
+        const map = {
             ".stream-description-editable": {
                 on_start: stream_edit.set_raw_description,
                 on_save: stream_edit.change_stream_description,
@@ -777,7 +777,7 @@ exports.initialize = function () {
             // if there are any child nodes, inclusive of <br> which means you
             // have lines in your description or title, you're doing something
             // wrong.
-            for (var x = 0; x < this.childNodes.length; x += 1) {
+            for (let x = 0; x < this.childNodes.length; x += 1) {
                 if (this.childNodes[x].nodeType !== 3) {
                     this.innerText = this.innerText.replace(/\n/, "");
                     break;
@@ -786,8 +786,8 @@ exports.initialize = function () {
         });
 
         $("body").on("click", "[data-make-editable]", function () {
-            var selector = $(this).attr("data-make-editable");
-            var edit_area = $(this).parent().find(selector);
+            const selector = $(this).attr("data-make-editable");
+            const edit_area = $(this).parent().find(selector);
             if (edit_area.attr("contenteditable") === "true") {
                 $("[data-finish-editing='" + selector + "']").hide();
                 edit_area.attr("contenteditable", false);
@@ -810,7 +810,7 @@ exports.initialize = function () {
         });
 
         $("body").on("click", "[data-finish-editing]", function (e) {
-            var selector = $(this).attr("data-finish-editing");
+            const selector = $(this).attr("data-finish-editing");
             if (map[selector].on_save) {
                 map[selector].on_save(e);
                 $(this).hide();
@@ -829,11 +829,11 @@ exports.initialize = function () {
         hotspots.close_hotspot_icon(this);
 
         // show popover
-        var hotspot_name = $(e.target).closest('.hotspot-icon')
+        const hotspot_name = $(e.target).closest('.hotspot-icon')
             .attr('id')
             .replace('hotspot_', '')
             .replace('_icon', '');
-        var overlay_name = 'hotspot_' + hotspot_name + '_overlay';
+        const overlay_name = 'hotspot_' + hotspot_name + '_overlay';
 
         overlays.open_overlay({
             name: overlay_name,
@@ -856,9 +856,9 @@ exports.initialize = function () {
         e.preventDefault();
         e.stopPropagation();
 
-        var overlay_name = $(this).closest('.hotspot.overlay').attr('id');
+        const overlay_name = $(this).closest('.hotspot.overlay').attr('id');
 
-        var hotspot_name = overlay_name
+        const hotspot_name = overlay_name
             .replace('hotspot_', '')
             .replace('_overlay', '');
 
diff --git a/static/js/copy_and_paste.js b/static/js/copy_and_paste.js
index 854f0dad00..ed1ea90431 100644
--- a/static/js/copy_and_paste.js
+++ b/static/js/copy_and_paste.js
@@ -1,9 +1,9 @@
 const TurndownService = require("turndown/lib/turndown.cjs.js");
 
 function find_boundary_tr(initial_tr, iterate_row) {
-    var j;
-    var skip_same_td_check = false;
-    var tr = initial_tr;
+    let j;
+    let skip_same_td_check = false;
+    let tr = initial_tr;
 
     // If the selection boundary is somewhere that does not have a
     // parent tr, we should let the browser handle the copy-paste
@@ -34,7 +34,7 @@ function find_boundary_tr(initial_tr, iterate_row) {
 }
 
 function construct_recipient_header(message_row) {
-    var message_header_content = rows.get_message_recipient_header(message_row)
+    const message_header_content = rows.get_message_recipient_header(message_row)
         .text()
         .replace(/\s+/g, " ")
         .replace(/^\s/, "").replace(/\s$/, "");
@@ -57,14 +57,14 @@ how modern browsers deal with copy/paste.  Just test
 your changes carefully.
 */
 function construct_copy_div(div, start_id, end_id) {
-    var start_row = current_msg_list.get_row(start_id);
-    var start_recipient_row = rows.get_message_recipient_row(start_row);
-    var start_recipient_row_id = rows.id_for_recipient_row(start_recipient_row);
-    var should_include_start_recipient_header = false;
+    const start_row = current_msg_list.get_row(start_id);
+    const start_recipient_row = rows.get_message_recipient_row(start_row);
+    const start_recipient_row_id = rows.id_for_recipient_row(start_recipient_row);
+    let should_include_start_recipient_header = false;
 
-    var last_recipient_row_id = start_recipient_row_id;
-    for (var row = start_row; rows.id(row) <= end_id; row = rows.next_visible(row)) {
-        var recipient_row_id = rows.id_for_recipient_row(rows.get_message_recipient_row(row));
+    let last_recipient_row_id = start_recipient_row_id;
+    for (let row = start_row; rows.id(row) <= end_id; row = rows.next_visible(row)) {
+        const recipient_row_id = rows.id_for_recipient_row(rows.get_message_recipient_row(row));
         // if we found a message from another recipient,
         // it means that we have messages from several recipients,
         // so we have to add new recipient's bar to final copied message
@@ -74,8 +74,8 @@ function construct_copy_div(div, start_id, end_id) {
             last_recipient_row_id = recipient_row_id;
             should_include_start_recipient_header = true;
         }
-        var message = current_msg_list.get(rows.id(row));
-        var message_firstp = $(message.content).slice(0, 1);
+        const message = current_msg_list.get(rows.id(row));
+        const message_firstp = $(message.content).slice(0, 1);
         message_firstp.prepend(message.sender_full_name + ": ");
         div.append(message_firstp);
         div.append($(message.content).slice(1));
@@ -132,13 +132,13 @@ exports.copy_handler = function () {
     // * Otherwise, we want to copy the bodies of all messages that
     //   were partially covered by the selection.
 
-    var selection = window.getSelection();
-    var analysis = exports.analyze_selection(selection);
-    var ranges = analysis.ranges;
-    var start_id = analysis.start_id;
-    var end_id = analysis.end_id;
-    var skip_same_td_check = analysis.skip_same_td_check;
-    var div = $('<div>');
+    const selection = window.getSelection();
+    const analysis = exports.analyze_selection(selection);
+    const ranges = analysis.ranges;
+    const start_id = analysis.start_id;
+    const end_id = analysis.end_id;
+    const skip_same_td_check = analysis.skip_same_td_check;
+    const div = $('<div>');
 
     if (start_id === undefined || end_id === undefined) {
         // In this case either the starting message or the ending
@@ -186,20 +186,20 @@ exports.analyze_selection = function (selection) {
     // analyze the combined range of the selections, and copy their
     // full content.
 
-    var i;
-    var range;
-    var ranges = [];
-    var startc;
-    var endc;
-    var initial_end_tr;
-    var start_id;
-    var end_id;
-    var start_data;
-    var end_data;
+    let i;
+    let range;
+    const ranges = [];
+    let startc;
+    let endc;
+    let initial_end_tr;
+    let start_id;
+    let end_id;
+    let start_data;
+    let end_data;
     // skip_same_td_check is true whenever we know for a fact that the
     // selection covers multiple messages (and thus we should no
     // longer consider letting the browser handle the copy event).
-    var skip_same_td_check = false;
+    let skip_same_td_check = false;
 
     for (i = 0; i < selection.rangeCount; i += 1) {
         range = selection.getRangeAt(i);
@@ -297,7 +297,7 @@ exports.paste_handler_converter = function (paste_html) {
 };
 
 exports.paste_handler = function (event) {
-    var clipboardData = event.originalEvent.clipboardData;
+    const clipboardData = event.originalEvent.clipboardData;
     if (!clipboardData) {
         // On IE11, ClipboardData isn't defined.  One can instead
         // access it with `window.clipboardData`, but even that
@@ -308,10 +308,10 @@ exports.paste_handler = function (event) {
     }
 
     if (clipboardData.getData) {
-        var paste_html = clipboardData.getData('text/html');
+        const paste_html = clipboardData.getData('text/html');
         if (paste_html && page_params.development_environment) {
-            var text = exports.paste_handler_converter(paste_html);
-            var mdImageRegex = /^!\[.*\]\(.*\)$/;
+            const text = exports.paste_handler_converter(paste_html);
+            const mdImageRegex = /^!\[.*\]\(.*\)$/;
             if (text.match(mdImageRegex)) {
                 // This block catches cases where we are pasting an
                 // image into Zulip, which should be handled by the
diff --git a/static/js/hash_util.js b/static/js/hash_util.js
index f9394d0469..b75ec05e22 100644
--- a/static/js/hash_util.js
+++ b/static/js/hash_util.js
@@ -10,7 +10,7 @@ exports.get_hash_section = function (hash) {
         return '';
     }
 
-    var parts = hash.replace(/\/$/, "").split(/\//);
+    const parts = hash.replace(/\/$/, "").split(/\//);
 
     return parts[1] || '';
 };
@@ -26,7 +26,7 @@ exports.encodeHashComponent = function (str) {
 
 exports.encode_operand = function (operator, operand) {
     if (operator === 'group-pm-with' || operator === 'pm-with' || operator === 'sender') {
-        var slug = people.emails_to_slug(operand);
+        const slug = people.emails_to_slug(operand);
         if (slug) {
             return slug;
         }
@@ -42,7 +42,7 @@ exports.encode_operand = function (operator, operand) {
 exports.encode_stream_id = function (stream_id) {
     // stream_data appends the stream name, but it does not do the
     // URI encoding piece
-    var slug = stream_data.id_to_slug(stream_id);
+    const slug = stream_data.id_to_slug(stream_id);
 
     return exports.encodeHashComponent(slug);
 };
@@ -61,7 +61,7 @@ exports.decodeHashComponent = function (str) {
 
 exports.decode_operand = function (operator, operand) {
     if (operator === 'group-pm-with' || operator === 'pm-with' || operator === 'sender') {
-        var emails = people.slug_to_emails(operand);
+        const emails = people.slug_to_emails(operand);
         if (emails) {
             return emails;
         }
@@ -89,16 +89,16 @@ exports.by_stream_topic_uri = function (stream_id, topic) {
 // corresponding hash: the # component
 // of the narrow URL
 exports.operators_to_hash = function (operators) {
-    var hash = '#';
+    let hash = '#';
 
     if (operators !== undefined) {
         hash = '#narrow';
         _.each(operators, function (elem) {
             // Support legacy tuples.
-            var operator = elem.operator;
-            var operand = elem.operand;
+            const operator = elem.operator;
+            const operand = elem.operand;
 
-            var sign = elem.negated ? '-' : '';
+            const sign = elem.negated ? '-' : '';
             hash += '/' + sign + exports.encodeHashComponent(operator)
                   + '/' + exports.encode_operand(operator, operand);
         });
@@ -128,11 +128,11 @@ exports.huddle_with_uri = function (user_ids_string) {
 };
 
 exports.by_conversation_and_time_uri = function (message) {
-    var absolute_url = window.location.protocol + "//" +
+    const absolute_url = window.location.protocol + "//" +
         window.location.host + "/" +
         window.location.pathname.split('/')[1];
 
-    var suffix = "/near/" + exports.encodeHashComponent(message.id);
+    const suffix = "/near/" + exports.encodeHashComponent(message.id);
 
     if (message.type === "stream") {
         return absolute_url +
@@ -144,30 +144,30 @@ exports.by_conversation_and_time_uri = function (message) {
 };
 
 exports.stream_edit_uri = function (sub) {
-    var hash = "#streams" + "/" + sub.stream_id + "/" + exports.encodeHashComponent(sub.name);
+    const hash = "#streams" + "/" + sub.stream_id + "/" + exports.encodeHashComponent(sub.name);
     return hash;
 };
 
 exports.parse_narrow = function (hash) {
-    var i;
-    var operators = [];
+    let i;
+    const operators = [];
     for (i = 1; i < hash.length; i += 2) {
         // We don't construct URLs with an odd number of components,
         // but the user might write one.
-        var operator = exports.decodeHashComponent(hash[i]);
+        let operator = exports.decodeHashComponent(hash[i]);
         // Do not parse further if empty operator encountered.
         if (operator === '') {
             break;
         }
 
-        var raw_operand = hash[i + 1];
+        const raw_operand = hash[i + 1];
 
         if (!raw_operand) {
             return;
         }
 
-        var operand  = exports.decode_operand(operator, raw_operand);
-        var negated = false;
+        const operand  = exports.decode_operand(operator, raw_operand);
+        let negated = false;
         if (operator[0] === '-') {
             negated = true;
             operator = operator.slice(1);
diff --git a/static/js/message_list_view.js b/static/js/message_list_view.js
index b222eca92e..cbd4e16e94 100644
--- a/static/js/message_list_view.js
+++ b/static/js/message_list_view.js
@@ -1,7 +1,7 @@
-var render_bookend = require('../templates/bookend.hbs');
-var render_message_group = require('../templates/message_group.hbs');
-var render_recipient_row = require('../templates/recipient_row.hbs');
-var render_single_message = require('../templates/single_message.hbs');
+const render_bookend = require('../templates/bookend.hbs');
+const render_message_group = require('../templates/message_group.hbs');
+const render_recipient_row = require('../templates/recipient_row.hbs');
+const render_single_message = require('../templates/single_message.hbs');
 
 function MessageListView(list, table_name, collapse_messages) {
     this.list = list;
@@ -20,10 +20,10 @@ function MessageListView(list, table_name, collapse_messages) {
 }
 
 function get_user_id_for_mention_button(elem) {
-    var user_id = $(elem).attr('data-user-id');
+    const user_id = $(elem).attr('data-user-id');
     // Handle legacy markdown that was rendered before we cut
     // over to using data-user-id.
-    var email = $(elem).attr('data-user-email');
+    const email = $(elem).attr('data-user-email');
 
     if (user_id === "*" || email === "*") {
         return "*";
@@ -35,7 +35,7 @@ function get_user_id_for_mention_button(elem) {
 
     if (email) {
         // Will return undefined if there's no match
-        var user = people.get_by_email(email);
+        const user = people.get_by_email(email);
         if (user) {
             return user.user_id;
         }
@@ -45,7 +45,7 @@ function get_user_id_for_mention_button(elem) {
 }
 
 function get_user_group_id_for_mention_button(elem) {
-    var user_group_id = $(elem).attr('data-user-group-id');
+    const user_group_id = $(elem).attr('data-user-group-id');
 
     if (user_group_id) {
         return user_group_id;
@@ -58,8 +58,8 @@ function same_day(earlier_msg, later_msg) {
     if (earlier_msg === undefined || later_msg === undefined) {
         return false;
     }
-    var earlier_time = new XDate(earlier_msg.msg.timestamp * 1000);
-    var later_time = new XDate(later_msg.msg.timestamp * 1000);
+    const earlier_time = new XDate(earlier_msg.msg.timestamp * 1000);
+    const later_time = new XDate(later_msg.msg.timestamp * 1000);
 
     return earlier_time.toDateString() === later_time.toDateString();
 }
@@ -79,19 +79,19 @@ function same_recipient(a, b) {
 }
 
 function render_group_display_date(group, message_container) {
-    var time = new XDate(message_container.msg.timestamp * 1000);
-    var today = new XDate();
-    var date_element = timerender.render_date(time, undefined, today)[0];
+    const time = new XDate(message_container.msg.timestamp * 1000);
+    const today = new XDate();
+    const date_element = timerender.render_date(time, undefined, today)[0];
 
     group.date = date_element.outerHTML;
 }
 
 function update_group_date_divider(group, message_container, prev) {
-    var time = new XDate(message_container.msg.timestamp * 1000);
-    var today = new XDate();
+    const time = new XDate(message_container.msg.timestamp * 1000);
+    const today = new XDate();
 
     if (prev !== undefined) {
-        var prev_time = new XDate(prev.msg.timestamp * 1000);
+        const prev_time = new XDate(prev.msg.timestamp * 1000);
         if (time.toDateString() !== prev_time.toDateString()) {
             // NB: group_date_divider_html is HTML, inserted into the document without escaping.
             group.group_date_divider_html = timerender.render_date(time, prev_time,
@@ -118,17 +118,17 @@ function clear_message_date_divider(msg) {
 }
 
 function update_message_date_divider(opts) {
-    var prev_msg_container = opts.prev_msg_container;
-    var curr_msg_container = opts.curr_msg_container;
+    const prev_msg_container = opts.prev_msg_container;
+    const curr_msg_container = opts.curr_msg_container;
 
     if (!prev_msg_container || same_day(curr_msg_container, prev_msg_container)) {
         clear_message_date_divider(curr_msg_container);
         return;
     }
 
-    var prev_time = new XDate(prev_msg_container.msg.timestamp * 1000);
-    var curr_time = new XDate(curr_msg_container.msg.timestamp * 1000);
-    var today = new XDate();
+    const prev_time = new XDate(prev_msg_container.msg.timestamp * 1000);
+    const curr_time = new XDate(curr_msg_container.msg.timestamp * 1000);
+    const today = new XDate();
 
     curr_msg_container.want_date_divider = true;
     curr_msg_container.date_divider_html =
@@ -136,7 +136,7 @@ function update_message_date_divider(opts) {
 }
 
 function set_timestr(message_container) {
-    var time = new XDate(message_container.msg.timestamp * 1000);
+    const time = new XDate(message_container.msg.timestamp * 1000);
     message_container.timestr = timerender.stringify_time(time);
 }
 
@@ -166,7 +166,7 @@ function populate_group_from_message_container(group, message_container) {
         group.match_topic = util.get_match_topic(message_container.msg);
         group.stream_url = message_container.stream_url;
         group.topic_url = message_container.topic_url;
-        var sub = stream_data.get_sub(message_container.msg.stream);
+        const sub = stream_data.get_sub(message_container.msg.stream);
         if (sub === undefined) {
             // Hack to handle unusual cases like the tutorial where
             // the streams used don't actually exist in the subs
@@ -196,8 +196,8 @@ MessageListView.prototype = {
 
     _get_msg_timestring: function (message_container) {
         if (message_container.msg.last_edit_timestamp !== undefined) {
-            var last_edit_time = new XDate(message_container.msg.last_edit_timestamp * 1000);
-            var today = new XDate();
+            const last_edit_time = new XDate(message_container.msg.last_edit_timestamp * 1000);
+            const today = new XDate();
             return timerender.render_date(last_edit_time, undefined, today)[0].textContent +
                 " at " + timerender.stringify_time(last_edit_time);
         }
@@ -211,9 +211,9 @@ MessageListView.prototype = {
         //   * `edited_in_left_col`      -- when label appears in left column.
         //   * `edited_alongside_sender` -- when label appears alongside sender info.
         //   * `edited_status_msg`       -- when label appears for a "/me" message.
-        var last_edit_timestr = this._get_msg_timestring(message_container);
-        var include_sender = message_container.include_sender;
-        var status_message = Boolean(message_container.status_message);
+        const last_edit_timestr = this._get_msg_timestring(message_container);
+        const include_sender = message_container.include_sender;
+        const status_message = Boolean(message_container.status_message);
         if (last_edit_timestr !== undefined) {
             message_container.last_edit_timestr = last_edit_timestr;
             message_container.edited_in_left_col = !include_sender;
@@ -227,9 +227,9 @@ MessageListView.prototype = {
             return;
         }
 
-        var last_subscribed = !last_msg_container.msg.historical;
-        var first_subscribed = !first_msg_container.msg.historical;
-        var stream = first_msg_container.msg.stream;
+        const last_subscribed = !last_msg_container.msg.historical;
+        const first_subscribed = !first_msg_container.msg.historical;
+        const stream = first_msg_container.msg.stream;
 
         if (!last_subscribed && first_subscribed) {
             group.bookend_top = true;
@@ -254,10 +254,10 @@ MessageListView.prototype = {
             };
         }
 
-        var self = this;
-        var current_group = start_group();
-        var new_message_groups = [];
-        var prev;
+        const self = this;
+        let current_group = start_group();
+        const new_message_groups = [];
+        let prev;
 
         function add_message_container_to_group(message_container) {
             if (same_sender(prev, message_container)) {
@@ -278,7 +278,7 @@ MessageListView.prototype = {
         }
 
         _.each(message_containers, function (message_container) {
-            var message_reactions = reactions.get_message_reactions(message_container.msg);
+            const message_reactions = reactions.get_message_reactions(message_container.msg);
             message_container.msg.message_reactions = message_reactions;
             message_container.include_recipient = false;
             message_container.include_footer    = false;
@@ -364,8 +364,8 @@ MessageListView.prototype = {
         if (first_group === undefined || second_group === undefined) {
             return false;
         }
-        var last_msg_container = _.last(first_group.message_containers);
-        var first_msg_container = _.first(second_group.message_containers);
+        const last_msg_container = _.last(first_group.message_containers);
+        const first_msg_container = _.first(second_group.message_containers);
 
         // Join two groups into one.
         if (this.collapse_messages && same_recipient(last_msg_container, first_msg_container) &&
@@ -403,17 +403,17 @@ MessageListView.prototype = {
         // append_messages are messages which should be added to the last group in the DOM
         // rerender_messages are messages which should be updated in place in the DOM
 
-        var message_actions = {
+        const message_actions = {
             append_groups: [],
             prepend_groups: [],
             rerender_groups: [],
             append_messages: [],
             rerender_messages_next_same_sender: [],
         };
-        var first_group;
-        var second_group;
-        var curr_msg_container;
-        var prev_msg_container;
+        let first_group;
+        let second_group;
+        let curr_msg_container;
+        let prev_msg_container;
 
         if (where === 'top') {
             first_group = _.last(new_message_groups);
@@ -431,7 +431,7 @@ MessageListView.prototype = {
             curr_msg_container = _.first(second_group.message_containers);
         }
 
-        var was_joined = this.join_message_groups(first_group, second_group);
+        const was_joined = this.join_message_groups(first_group, second_group);
         if (was_joined) {
             update_message_date_divider({
                 prev_msg_container: prev_msg_container,
@@ -501,9 +501,9 @@ MessageListView.prototype = {
             blueslip.error('programming error--pass in jQuery objects');
         }
 
-        var self = this;
+        const self = this;
         _.each($message_rows, function (dom_row) {
-            var row = $(dom_row);
+            const row = $(dom_row);
             self._put_row(row);
             self._post_process_single_row(row);
         });
@@ -521,7 +521,7 @@ MessageListView.prototype = {
             blueslip.error('programming error--expected single element');
         }
 
-        var content = row.find('.message_content');
+        const content = row.find('.message_content');
 
         // Set the rtl class if the text has an rtl direction
         if (rtl.get_direction(content.text()) === 'rtl') {
@@ -529,7 +529,7 @@ MessageListView.prototype = {
         }
 
         content.find('.user-mention').each(function () {
-            var user_id = get_user_id_for_mention_button(this);
+            const user_id = get_user_id_for_mention_button(this);
             // We give special highlights to the mention buttons
             // that refer to the current user.
             if (user_id === "*" || people.is_my_user_id(user_id)) {
@@ -541,7 +541,7 @@ MessageListView.prototype = {
                 // mention text to show the user's current name,
                 // assuming that you're not searching for text
                 // inside the highlight.
-                var person = people.get_person_from_user_id(user_id);
+                const person = people.get_person_from_user_id(user_id);
                 if (person !== undefined) {
                     // Note that person might be undefined in some
                     // unpleasant corner cases involving data import.
@@ -551,8 +551,8 @@ MessageListView.prototype = {
         });
 
         content.find('.user-group-mention').each(function () {
-            var user_group_id = get_user_group_id_for_mention_button(this);
-            var user_group = user_groups.get_user_group_from_id(user_group_id, true);
+            const user_group_id = get_user_group_id_for_mention_button(this);
+            const user_group = user_groups.get_user_group_from_id(user_group_id, true);
             if (user_group === undefined) {
                 // This is a user group the current user doesn't have
                 // data on.  This can happen when user groups are
@@ -561,7 +561,7 @@ MessageListView.prototype = {
                 return;
             }
 
-            var my_user_id = people.my_current_user_id();
+            const my_user_id = people.my_current_user_id();
             // Mark user group you're a member of.
             if (user_groups.is_member_of(user_group_id, my_user_id)) {
                 $(this).addClass('user-mention-me');
@@ -575,7 +575,7 @@ MessageListView.prototype = {
         });
 
         content.find('a.stream').each(function () {
-            var stream_id = $(this).attr('data-stream-id');
+            const stream_id = $(this).attr('data-stream-id');
             if (stream_id && !$(this).find(".highlight").length) {
                 // Display the current name for stream if it is not
                 // being displayed in search highlight.
@@ -584,12 +584,12 @@ MessageListView.prototype = {
         });
 
         content.find('a.stream-topic').each(function () {
-            var stream_id = $(this).attr('data-stream-id');
+            const stream_id = $(this).attr('data-stream-id');
             if (stream_id && !$(this).find(".highlight").length) {
                 // Display the current name for stream if it is not
                 // being displayed in search highlight.
-                var text = $(this).text();
-                var topic = text.split('>', 2)[1];
+                const text = $(this).text();
+                const topic = text.split('>', 2)[1];
                 $(this).text("#" + stream_data.maybe_get_stream_name(stream_id) + ' > ' + topic);
             }
         });
@@ -598,12 +598,12 @@ MessageListView.prototype = {
         // page_params.emojiset is 'text'.
         if (page_params.emojiset === 'text') {
             content.find(".emoji").replaceWith(function () {
-                var text = $(this).attr("title");
+                const text = $(this).attr("title");
                 return ":" + text + ":";
             });
         }
 
-        var id = rows.id(row);
+        const id = rows.id(row);
         message_edit.maybe_show_edit(row, id);
 
         submessage.process_submessages({
@@ -613,18 +613,18 @@ MessageListView.prototype = {
     },
 
     _get_message_template: function (message_container) {
-        var msg_reactions = reactions.get_message_reactions(message_container.msg);
+        const msg_reactions = reactions.get_message_reactions(message_container.msg);
         message_container.msg.message_reactions = msg_reactions;
-        var msg_to_render = _.extend(message_container, {
+        const msg_to_render = _.extend(message_container, {
             table_name: this.table_name,
         });
         return render_single_message(msg_to_render);
     },
 
     _render_group: function (opts) {
-        var message_groups = opts.message_groups;
-        var use_match_properties = opts.use_match_properties;
-        var table_name = opts.table_name;
+        const message_groups = opts.message_groups;
+        const use_match_properties = opts.use_match_properties;
+        const table_name = opts.table_name;
 
         return $(render_message_group({
             message_groups: message_groups,
@@ -639,22 +639,22 @@ MessageListView.prototype = {
 
         // Store this in a separate variable so it doesn't get
         // confusingly masked in upcoming loops.
-        var self = this;
+        const self = this;
 
         if (messages.length === 0 || self.table_name === undefined) {
             return;
         }
 
-        var list = self.list; // for convenience
-        var table_name = self.table_name;
-        var table = rows.get_table(table_name);
-        var orig_scrolltop_offset;
+        const list = self.list; // for convenience
+        const table_name = self.table_name;
+        const table = rows.get_table(table_name);
+        let orig_scrolltop_offset;
 
         // If we start with the message feed scrolled up (i.e.
         // the bottom message is not visible), then we will respect
         // the user's current position after rendering, rather
         // than auto-scrolling.
-        var started_scrolled_up = message_viewport.is_scrolled_up();
+        const started_scrolled_up = message_viewport.is_scrolled_up();
 
         // The messages we are being asked to render are shared with between
         // all messages lists. To prevent having both list views overwriting
@@ -690,13 +690,13 @@ MessageListView.prototype = {
             return;
         }
 
-        var new_message_groups = self.build_message_groups(message_containers, self.table_name);
-        var message_actions = self.merge_message_groups(new_message_groups, where);
-        var new_dom_elements = [];
-        var rendered_groups;
-        var dom_messages;
-        var last_message_row;
-        var last_group_row;
+        const new_message_groups = self.build_message_groups(message_containers, self.table_name);
+        const message_actions = self.merge_message_groups(new_message_groups, where);
+        let new_dom_elements = [];
+        let rendered_groups;
+        let dom_messages;
+        let last_message_row;
+        let last_group_row;
 
         _.each(message_containers, function (message_container) {
             self.message_containers[message_container.msg.id] = message_container;
@@ -729,7 +729,7 @@ MessageListView.prototype = {
             save_scroll_position();
 
             _.each(message_actions.rerender_groups, function (message_group) {
-                var old_message_group = $('#' + message_group.message_group_id);
+                const old_message_group = $('#' + message_group.message_group_id);
                 // Remove the top date_row, we'll re-add it after rendering
                 old_message_group.prev('.date_row').remove();
 
@@ -756,9 +756,9 @@ MessageListView.prototype = {
         // entirely, since it appears the next_is_same_sender CSS
         // class doesn't do anything.
         if (message_actions.rerender_messages_next_same_sender.length > 0) {
-            var targets = message_actions.rerender_messages_next_same_sender;
+            const targets = message_actions.rerender_messages_next_same_sender;
             _.each(targets, function (message_container) {
-                var row = self.get_row(message_container.msg.id);
+                const row = self.get_row(message_container.msg.id);
                 $(row).find("div.messagebox").toggleClass("next_is_same_sender",
                                                           message_container.next_is_same_sender);
             });
@@ -815,17 +815,17 @@ MessageListView.prototype = {
 
         restore_scroll_position();
 
-        var last_message_group = _.last(self._message_groups);
+        const last_message_group = _.last(self._message_groups);
         if (last_message_group !== undefined) {
             list.last_message_historical =
                 _.last(last_message_group.message_containers).msg.historical;
         }
 
-        var stream_name = narrow_state.stream();
+        const stream_name = narrow_state.stream();
         if (stream_name !== undefined) {
             // If user narrows to a stream, doesn't update
             // trailing bookend if user is subscribed.
-            var sub = stream_data.get_sub(stream_name);
+            const sub = stream_data.get_sub(stream_name);
             if (sub === undefined || !sub.subscribed) {
                 list.update_trailing_bookend();
             }
@@ -834,12 +834,12 @@ MessageListView.prototype = {
         if (list === current_msg_list) {
             // Update the fade.
 
-            var get_element = function (message_group) {
+            const get_element = function (message_group) {
                 // We don't have a MessageGroup class, but we can at least hide the messy details
                 // of rows.js from compose_fade.  We provide a callback function to be lazy--
                 // compose_fade may not actually need the elements depending on its internal
                 // state.
-                var message_row = self.get_row(message_group.message_containers[0].msg.id);
+                const message_row = self.get_row(message_group.message_containers[0].msg.id);
                 return rows.get_message_recipient_row(message_row);
             };
 
@@ -850,8 +850,8 @@ MessageListView.prototype = {
             // First, in single-recipient narrows, potentially
             // auto-scroll to the latest message if it was sent by us.
             if (narrow_state.narrowed_by_reply()) {
-                var selected_id = list.selected_id();
-                var i;
+                const selected_id = list.selected_id();
+                let i;
 
                 // Iterate backwards to find the last message
                 // sent_by_me, stopping at the pointer position.
@@ -859,7 +859,7 @@ MessageListView.prototype = {
                 // should be limited in how far offscreen it's willing
                 // to go.
                 for (i = messages.length - 1; i >= 0; i -= 1) {
-                    var id = messages[i].id;
+                    const id = messages[i].id;
                     if (id <= selected_id) {
                         break;
                     }
@@ -878,8 +878,8 @@ MessageListView.prototype = {
                     need_user_to_scroll: true,
                 };
             }
-            var new_messages_height = self._new_messages_height(new_dom_elements);
-            var need_user_to_scroll = self._maybe_autoscroll(new_messages_height);
+            const new_messages_height = self._new_messages_height(new_dom_elements);
+            const need_user_to_scroll = self._maybe_autoscroll(new_messages_height);
 
             if (need_user_to_scroll) {
                 return {
@@ -890,8 +890,8 @@ MessageListView.prototype = {
     },
 
     _new_messages_height: function (rendered_elems) {
-        var new_messages_height = 0;
-        var id_of_last_message_sent_by_us = -1;
+        let new_messages_height = 0;
+        let id_of_last_message_sent_by_us = -1;
 
         // C++ iterators would have made this less painful
         _.each(rendered_elems.reverse(), function (elem) {
@@ -903,7 +903,7 @@ MessageListView.prototype = {
                 if (id_of_last_message_sent_by_us > -1) {
                     return;
                 }
-                var row_id = rows.id(elem);
+                const row_id = rows.id(elem);
                 // check for `row_id` NaN in case we're looking at a date row or bookend row
                 if (row_id > -1 &&
                     people.is_current_user(this.get_message(row_id).sender_email)) {
@@ -920,8 +920,8 @@ MessageListView.prototype = {
         // it's the max amount that we can scroll down (or "skooch
         // up" the messages) before knocking the selected message
         // out of the feed.
-        var selected_row_top = selected_row.offset().top;
-        var scroll_limit = selected_row_top - viewport_info.visible_top;
+        const selected_row_top = selected_row.offset().top;
+        let scroll_limit = selected_row_top - viewport_info.visible_top;
 
         if (scroll_limit < 0) {
             // This shouldn't happen, but if we're off by a pixel or
@@ -940,8 +940,8 @@ MessageListView.prototype = {
         //
         // returns `true` if we need the user to scroll
 
-        var selected_row = this.selected_row();
-        var last_visible = rows.last_visible();
+        const selected_row = this.selected_row();
+        const last_visible = rows.last_visible();
 
         // Make sure we have a selected row and last visible row. (defensive)
         if (!(selected_row && selected_row.length > 0 && last_visible)) {
@@ -971,8 +971,8 @@ MessageListView.prototype = {
             return false;
         }
 
-        var info = message_viewport.message_viewport_info();
-        var scroll_limit = this._scroll_limit(selected_row, info);
+        const info = message_viewport.message_viewport_info();
+        const scroll_limit = this._scroll_limit(selected_row, info);
 
         // This next decision is fairly debatable.  For a big message that
         // would push the pointer off the screen, we do a partial autoscroll,
@@ -982,8 +982,8 @@ MessageListView.prototype = {
         //    c) scroll amount isn't really tied to size of new messages (bad)
         //    d) all the bad things about scrolling for users who want messages
         //       to stay on the screen
-        var scroll_amount;
-        var need_user_to_scroll;
+        let scroll_amount;
+        let need_user_to_scroll;
 
         if (new_messages_height <= scroll_limit) {
             // This is the happy path where we can just scroll
@@ -997,7 +997,7 @@ MessageListView.prototype = {
             // (Even if we are somewhat constrained here, the message may
             // still end up being visible, so we do some arithmetic.)
             scroll_amount = scroll_limit;
-            var offset = message_viewport.offset_from_bottom(last_visible);
+            const offset = message_viewport.offset_from_bottom(last_visible);
 
             // For determining whether we need to show the user a "you
             // need to scroll down" notification, the obvious check
@@ -1011,11 +1011,11 @@ MessageListView.prototype = {
             // this notification, we need to adjust by the amount that
             // the current compose is bigger than the empty, open
             // compose box.
-            var compose_textarea_default_height = 42;
-            var compose_textarea_current_height = $("#compose-textarea").height();
-            var expected_change =
+            const compose_textarea_default_height = 42;
+            const compose_textarea_current_height = $("#compose-textarea").height();
+            const expected_change =
                 compose_textarea_current_height - compose_textarea_default_height;
-            var expected_offset = offset - expected_change;
+            const expected_offset = offset - expected_change;
             need_user_to_scroll = expected_offset > scroll_amount;
         }
 
@@ -1039,7 +1039,7 @@ MessageListView.prototype = {
     },
 
     update_render_window: function (selected_idx, check_for_changed) {
-        var new_start = Math.max(selected_idx - this._RENDER_WINDOW_SIZE / 2, 0);
+        const new_start = Math.max(selected_idx - this._RENDER_WINDOW_SIZE / 2, 0);
         if (check_for_changed && new_start === this._render_win_start) {
             return false;
         }
@@ -1056,7 +1056,7 @@ MessageListView.prototype = {
             return false;
         }
 
-        var selected_idx = this.list.selected_idx();
+        const selected_idx = this.list.selected_idx();
 
         // We rerender under the following conditions:
         // * The selected message is within this._RENDER_THRESHOLD messages
@@ -1085,9 +1085,9 @@ MessageListView.prototype = {
     rerender_preserving_scrolltop: function (discard_rendering_state) {
         // old_offset is the number of pixels between the top of the
         // viewable window and the selected message
-        var old_offset;
-        var selected_row = this.selected_row();
-        var selected_in_view = selected_row.length > 0;
+        let old_offset;
+        const selected_row = this.selected_row();
+        const selected_in_view = selected_row.length > 0;
         if (selected_in_view) {
             old_offset = selected_row.offset().top;
         }
@@ -1102,7 +1102,7 @@ MessageListView.prototype = {
     },
 
     set_message_offset: function (offset) {
-        var msg = this.selected_row();
+        const msg = this.selected_row();
         message_viewport.scrollTop(message_viewport.scrollTop() + msg.offset().top - offset);
     },
 
@@ -1148,23 +1148,23 @@ MessageListView.prototype = {
             return;
         }
 
-        var first_row = this.get_row(message_containers[0].msg.id);
+        const first_row = this.get_row(message_containers[0].msg.id);
 
         // We may not have the row if the stream or topic was muted
         if (first_row.length === 0) {
             return;
         }
 
-        var recipient_row = rows.get_message_recipient_row(first_row);
-        var header = recipient_row.find('.message_header');
-        var message_group_id = recipient_row.attr("id");
+        const recipient_row = rows.get_message_recipient_row(first_row);
+        const header = recipient_row.find('.message_header');
+        const message_group_id = recipient_row.attr("id");
 
         // Since there might be multiple dates within the message
         // group, it's important to lookup the original/full message
         // group rather than doing an artificial rerendering of the
         // message header from the set of message containers passed in
         // here.
-        var group = this._find_message_group(message_group_id);
+        const group = this._find_message_group(message_group_id);
         if (group === undefined) {
             blueslip.error("Could not find message group for rerendering headers");
             return;
@@ -1176,14 +1176,14 @@ MessageListView.prototype = {
         // rerendering rather than looking up the original version.
         populate_group_from_message_container(group, group.message_containers[0]);
 
-        var rendered_recipient_row = $(render_recipient_row(group));
+        const rendered_recipient_row = $(render_recipient_row(group));
 
         header.replaceWith(rendered_recipient_row);
     },
 
     _rerender_message: function (message_container, message_content_edited) {
-        var row = this.get_row(message_container.msg.id);
-        var was_selected = this.list.selected_message() === message_container.msg;
+        const row = this.get_row(message_container.msg.id);
+        const was_selected = this.list.selected_message() === message_container.msg;
 
         // Re-render just this one message
         this._maybe_format_me_message(message_container);
@@ -1192,7 +1192,7 @@ MessageListView.prototype = {
         // Make sure the right thing happens if the message was edited to mention us.
         message_container.contains_mention = message_container.msg.mentioned;
 
-        var rendered_msg = $(this._get_message_template(message_container));
+        const rendered_msg = $(this._get_message_template(message_container));
         if (message_content_edited) {
             rendered_msg.addClass("fade-in-message");
         }
@@ -1205,10 +1205,10 @@ MessageListView.prototype = {
     },
 
     rerender_messages: function (messages, message_content_edited) {
-        var self = this;
+        const self = this;
 
         // Convert messages to list messages
-        var message_containers = _.map(messages, function (message) {
+        let message_containers = _.map(messages, function (message) {
             return self.message_containers[message.id];
         });
         // We may not have the message_container if the stream or topic was muted
@@ -1216,8 +1216,8 @@ MessageListView.prototype = {
             return message_container === undefined;
         });
 
-        var message_groups = [];
-        var current_group = [];
+        const message_groups = [];
+        let current_group = [];
         _.each(message_containers, function (message_container) {
             if (current_group.length === 0 ||
                 same_recipient(current_group[current_group.length - 1], message_container)) {
@@ -1237,11 +1237,11 @@ MessageListView.prototype = {
     },
 
     append: function (messages, messages_are_new) {
-        var cur_window_size = this._render_win_end - this._render_win_start;
-        var render_info;
+        const cur_window_size = this._render_win_end - this._render_win_start;
+        let render_info;
 
         if (cur_window_size < this._RENDER_WINDOW_SIZE) {
-            var slice_to_render = messages.slice(0, this._RENDER_WINDOW_SIZE - cur_window_size);
+            const slice_to_render = messages.slice(0, this._RENDER_WINDOW_SIZE - cur_window_size);
             render_info = this.render(slice_to_render, 'bottom', messages_are_new);
             this._render_win_end += slice_to_render.length;
         }
@@ -1251,7 +1251,7 @@ MessageListView.prototype = {
         // newly received message should trigger a rerender so that
         // the new message, which will appear in the viewable area,
         // is rendered.
-        var needed_rerender = this.maybe_rerender();
+        const needed_rerender = this.maybe_rerender();
 
         if (needed_rerender) {
             render_info = {need_user_to_scroll: true};
@@ -1264,10 +1264,10 @@ MessageListView.prototype = {
         this._render_win_start += messages.length;
         this._render_win_end += messages.length;
 
-        var cur_window_size = this._render_win_end - this._render_win_start;
+        const cur_window_size = this._render_win_end - this._render_win_start;
         if (cur_window_size < this._RENDER_WINDOW_SIZE) {
-            var msgs_to_render_count = this._RENDER_WINDOW_SIZE - cur_window_size;
-            var slice_to_render = messages.slice(messages.length - msgs_to_render_count);
+            const msgs_to_render_count = this._RENDER_WINDOW_SIZE - cur_window_size;
+            const slice_to_render = messages.slice(messages.length - msgs_to_render_count);
             this.render(slice_to_render, 'top', false);
             this._render_win_start -= slice_to_render.length;
         }
@@ -1287,7 +1287,7 @@ MessageListView.prototype = {
     },
 
     get_row: function (id) {
-        var row = this._rows[id];
+        const row = this._rows[id];
 
         if (row === undefined) {
             // For legacy reasons we need to return an empty
@@ -1299,12 +1299,12 @@ MessageListView.prototype = {
     },
 
     clear_trailing_bookend: function () {
-        var trailing_bookend = rows.get_table(this.table_name).find('.trailing_bookend');
+        const trailing_bookend = rows.get_table(this.table_name).find('.trailing_bookend');
         trailing_bookend.remove();
     },
 
     render_trailing_bookend: function (trailing_bookend_content, subscribed, show_button) {
-        var rendered_trailing_bookend = $(render_bookend({
+        const rendered_trailing_bookend = $(render_bookend({
             bookend_content: trailing_bookend_content,
             trailing: show_button,
             subscribed: subscribed,
@@ -1322,7 +1322,7 @@ MessageListView.prototype = {
 
     change_message_id: function (old_id, new_id) {
         if (this._rows[old_id] !== undefined) {
-            var row = this._rows[old_id];
+            const row = this._rows[old_id];
             delete this._rows[old_id];
 
             row.attr('zid', new_id);
@@ -1332,7 +1332,7 @@ MessageListView.prototype = {
         }
 
         if (this.message_containers[old_id] !== undefined) {
-            var message_container = this.message_containers[old_id];
+            const message_container = this.message_containers[old_id];
             delete this.message_containers[old_id];
             this.message_containers[new_id] = message_container;
         }
@@ -1344,8 +1344,8 @@ MessageListView.prototype = {
             // Slice the '<p>/me ' off the front, and '</p>' off the first line
             // 'p' tag is sliced off to get sender in the same line as the
             // first line of the message
-            var msg_content = message_container.msg.content;
-            var p_index = msg_content.indexOf('</p>');
+            const msg_content = message_container.msg.content;
+            const p_index = msg_content.indexOf('</p>');
             message_container.status_message = msg_content.slice('<p>/me '.length, p_index) +
                                                 msg_content.slice(p_index + '</p>'.length);
             message_container.include_sender = true;
diff --git a/static/js/narrow.js b/static/js/narrow.js
index 7a2a0578a1..fba8073948 100644
--- a/static/js/narrow.js
+++ b/static/js/narrow.js
@@ -1,4 +1,4 @@
-var unnarrow_times;
+let unnarrow_times;
 
 function report_narrow_time(initial_core_time, initial_free_time, network_time) {
     channel.post({
@@ -28,8 +28,8 @@ function report_unnarrow_time() {
         return;
     }
 
-    var initial_core_time = unnarrow_times.initial_core_time - unnarrow_times.start_time;
-    var initial_free_time = unnarrow_times.initial_free_time - unnarrow_times.start_time;
+    const initial_core_time = unnarrow_times.initial_core_time - unnarrow_times.start_time;
+    const initial_free_time = unnarrow_times.initial_free_time - unnarrow_times.start_time;
 
     channel.post({
         url: '/json/report/unnarrow_times',
@@ -58,8 +58,8 @@ exports.save_pre_narrow_offset_for_reload = function () {
 
 exports.narrow_title = "home";
 exports.activate = function (raw_operators, opts) {
-    var start_time = new Date();
-    var was_narrowed_already = narrow_state.active();
+    const start_time = new Date();
+    const was_narrowed_already = narrow_state.active();
     // most users aren't going to send a bunch of a out-of-narrow messages
     // and expect to visit a list of narrows, so let's get these out of the way.
     notifications.clear_compose_notifications();
@@ -71,8 +71,8 @@ exports.activate = function (raw_operators, opts) {
     if (raw_operators.length === 0) {
         return exports.deactivate();
     }
-    var filter = new Filter(raw_operators);
-    var operators = filter.operators();
+    const filter = new Filter(raw_operators);
+    const operators = filter.operators();
 
     // Take the most detailed part of the narrow to use as the title.
     // If the operator is something other than "stream", "topic", or
@@ -84,14 +84,14 @@ exports.activate = function (raw_operators, opts) {
             exports.narrow_title = filter.operands("stream")[0];
         }
     } else if (filter.has_operator("is")) {
-        var title = filter.operands("is")[0];
+        let title = filter.operands("is")[0];
         title = title.charAt(0).toUpperCase() + title.slice(1) + " messages";
         exports.narrow_title = title;
     } else if (filter.has_operator("pm-with") || filter.has_operator("group-pm-with")) {
-        var emails = filter.public_operators()[0].operand;
-        var user_ids = people.emails_strings_to_user_ids_string(emails);
+        const emails = filter.public_operators()[0].operand;
+        const user_ids = people.emails_strings_to_user_ids_string(emails);
         if (user_ids !== undefined) {
-            var names = people.get_recipients(user_ids);
+            const names = people.get_recipients(user_ids);
             if (filter.has_operator("pm-with")) {
                 exports.narrow_title = names;
             } else {
@@ -120,7 +120,7 @@ exports.activate = function (raw_operators, opts) {
         trigger: 'unknown',
     });
 
-    var id_info = {
+    const id_info = {
         target_id: undefined,
         local_select_id: undefined,
         final_select_id: undefined,
@@ -140,7 +140,7 @@ exports.activate = function (raw_operators, opts) {
         // having a near: narrow auto-reloaded.
         id_info.target_id = opts.then_select_id;
         if (opts.then_select_offset === undefined) {
-            var row = current_msg_list.get_row(opts.then_select_id);
+            const row = current_msg_list.get_row(opts.then_select_id);
             if (row.length > 0) {
                 opts.then_select_offset = row.offset().top;
             }
@@ -157,12 +157,12 @@ exports.activate = function (raw_operators, opts) {
     // reflect the upcoming narrow.
     narrow_state.set_current_filter(filter);
 
-    var muting_enabled = narrow_state.muting_enabled();
+    const muting_enabled = narrow_state.muting_enabled();
 
     // Save how far from the pointer the top of the message list was.
     exports.save_pre_narrow_offset_for_reload();
 
-    var msg_data =  new MessageListData({
+    let msg_data =  new MessageListData({
         filter: narrow_state.filter(),
         muting_enabled: muting_enabled,
     });
@@ -189,7 +189,7 @@ exports.activate = function (raw_operators, opts) {
         });
     }
 
-    var msg_list = new message_list.MessageList({
+    const msg_list = new message_list.MessageList({
         data: msg_data,
         table_name: 'zfilt',
         collapse_messages: !narrow_state.filter().is_search(),
@@ -208,16 +208,16 @@ exports.activate = function (raw_operators, opts) {
     message_list.set_narrowed(msg_list);
     current_msg_list = message_list.narrowed;
 
-    var then_select_offset;
+    let then_select_offset;
     if (id_info.target_id === id_info.final_select_id) {
         then_select_offset = opts.then_select_offset;
     }
 
-    var select_immediately = id_info.local_select_id !== undefined;
+    const select_immediately = id_info.local_select_id !== undefined;
 
     (function fetch_messages() {
-        var anchor;
-        var use_first_unread;
+        let anchor;
+        let use_first_unread;
 
         if (id_info.final_select_id !== undefined) {
             anchor = id_info.final_select_id;
@@ -266,7 +266,7 @@ exports.activate = function (raw_operators, opts) {
     if (page_params.search_pills_enabled && opts.trigger !== 'search') {
         search_pill_widget.widget.clear(true);
         _.each(operators, function (operator) {
-            var search_string = Filter.unparse([operator]);
+            const search_string = Filter.unparse([operator]);
             search_pill.append_search_string(search_string, search_pill_widget.widget);
         });
     }
@@ -295,7 +295,7 @@ exports.activate = function (raw_operators, opts) {
 
     compose_actions.on_narrow(opts);
 
-    var current_filter = narrow_state.filter();
+    const current_filter = narrow_state.filter();
 
     top_left_corner.handle_narrow_activated(current_filter);
     stream_list.handle_narrow_activated(current_filter);
@@ -325,7 +325,7 @@ function load_local_messages(msg_data) {
     // cases when our local cache (message_list.all) has at least
     // one message the user will expect to see in the new narrow.
 
-    var in_msgs = message_list.all.all_messages();
+    const in_msgs = message_list.all.all_messages();
     msg_data.add_messages(in_msgs);
 
     return !msg_data.empty();
@@ -337,9 +337,9 @@ exports.maybe_add_local_messages = function (opts) {
     //
     //  - update id_info with more complete values
     //  - add messages into our message list from our local cache
-    var id_info = opts.id_info;
-    var msg_data = opts.msg_data;
-    var unread_info = narrow_state.get_first_unread_info();
+    const id_info = opts.id_info;
+    const msg_data = opts.msg_data;
+    const unread_info = narrow_state.get_first_unread_info();
 
     if (unread_info.flavor === 'cannot_compute') {
         if (id_info.target_id) {
@@ -405,7 +405,7 @@ exports.maybe_add_local_messages = function (opts) {
         // is caught up, so the last message in our now-populated
         // msg_data object must be the last message matching the
         // narrow the server could give us, so we can render locally.
-        var last_msg = msg_data.last();
+        const last_msg = msg_data.last();
         id_info.final_select_id = last_msg.id;
         id_info.local_select_id = id_info.final_select_id;
         return;
@@ -445,19 +445,19 @@ exports.update_selection = function (opts) {
         return;
     }
 
-    var id_info = opts.id_info;
-    var select_offset = opts.select_offset;
+    const id_info = opts.id_info;
+    const select_offset = opts.select_offset;
 
-    var msg_id = id_info.final_select_id;
+    let msg_id = id_info.final_select_id;
     if (msg_id === undefined) {
         msg_id = message_list.narrowed.first_unread_message_id();
     }
 
-    var preserve_pre_narrowing_screen_position =
+    const preserve_pre_narrowing_screen_position =
         message_list.narrowed.get(msg_id) !== undefined &&
         select_offset !== undefined;
 
-    var then_scroll = !preserve_pre_narrowing_screen_position;
+    const then_scroll = !preserve_pre_narrowing_screen_position;
 
     message_list.narrowed.select_id(msg_id, {
         then_scroll: then_scroll,
@@ -478,7 +478,7 @@ exports.stream_topic = function () {
     // This function returns the stream/topic that we most
     // specifically care about, according (mostly) to the
     // currently selected message.
-    var msg = current_msg_list.selected_message();
+    const msg = current_msg_list.selected_message();
 
     if (msg) {
         return {
@@ -497,7 +497,7 @@ exports.stream_topic = function () {
 
 exports.activate_stream_for_cycle_hotkey = function (stream_name) {
     // This is the common code for A/D hotkeys.
-    var filter_expr = [
+    const filter_expr = [
         {operator: 'stream', operand: stream_name},
     ];
     exports.activate(filter_expr, {});
@@ -505,13 +505,13 @@ exports.activate_stream_for_cycle_hotkey = function (stream_name) {
 
 
 exports.stream_cycle_backward = function () {
-    var curr_stream = narrow_state.stream();
+    const curr_stream = narrow_state.stream();
 
     if (!curr_stream) {
         return;
     }
 
-    var stream_name = topic_generator.get_prev_stream(curr_stream);
+    const stream_name = topic_generator.get_prev_stream(curr_stream);
 
     if (!stream_name) {
         return;
@@ -521,13 +521,13 @@ exports.stream_cycle_backward = function () {
 };
 
 exports.stream_cycle_forward = function () {
-    var curr_stream = narrow_state.stream();
+    const curr_stream = narrow_state.stream();
 
     if (!curr_stream) {
         return;
     }
 
-    var stream_name = topic_generator.get_next_stream(curr_stream);
+    const stream_name = topic_generator.get_next_stream(curr_stream);
 
     if (!stream_name) {
         return;
@@ -537,13 +537,13 @@ exports.stream_cycle_forward = function () {
 };
 
 exports.narrow_to_next_topic = function () {
-    var curr_info = exports.stream_topic();
+    const curr_info = exports.stream_topic();
 
     if (!curr_info) {
         return;
     }
 
-    var next_narrow = topic_generator.get_next_topic(
+    const next_narrow = topic_generator.get_next_topic(
         curr_info.stream,
         curr_info.topic
     );
@@ -552,7 +552,7 @@ exports.narrow_to_next_topic = function () {
         return;
     }
 
-    var filter_expr = [
+    const filter_expr = [
         {operator: 'stream', operand: next_narrow.stream},
         {operator: 'topic', operand: next_narrow.topic},
     ];
@@ -562,9 +562,9 @@ exports.narrow_to_next_topic = function () {
 
 exports.narrow_to_next_pm_string = function () {
 
-    var curr_pm = narrow_state.pm_string();
+    const curr_pm = narrow_state.pm_string();
 
-    var next_pm = topic_generator.get_next_unread_pm_string(curr_pm);
+    const next_pm = topic_generator.get_next_unread_pm_string(curr_pm);
 
     if (!next_pm) {
         return;
@@ -572,14 +572,14 @@ exports.narrow_to_next_pm_string = function () {
 
     // Hopefully someday we can narrow by user_ids_string instead of
     // mapping back to emails.
-    var pm_with = people.user_ids_string_to_emails_string(next_pm);
+    const pm_with = people.user_ids_string_to_emails_string(next_pm);
 
-    var filter_expr = [
+    const filter_expr = [
         {operator: 'pm-with', operand: pm_with},
     ];
 
     // force_close parameter is true to not auto open compose_box
-    var opts = {
+    const opts = {
         force_close: true,
     };
 
@@ -595,7 +595,7 @@ exports.by = function (operator, operand, opts) {
 
 exports.by_topic = function (target_id, opts) {
     // don't use current_msg_list as it won't work for muted messages or for out-of-narrow links
-    var original = message_store.get(target_id);
+    const original = message_store.get(target_id);
     if (original.type !== 'stream') {
         // Only stream messages have topics, but the
         // user wants us to narrow in some way.
@@ -608,7 +608,7 @@ exports.by_topic = function (target_id, opts) {
     // message is about to be marked read in the new view.
     unread_ops.notify_server_message_read(original);
 
-    var search_terms = [
+    const search_terms = [
         {operator: 'stream', operand: original.stream},
         {operator: 'topic', operand: util.get_message_topic(original)},
     ];
@@ -620,7 +620,7 @@ exports.by_topic = function (target_id, opts) {
 exports.by_recipient = function (target_id, opts) {
     opts = _.defaults({}, opts, {then_select_id: target_id});
     // don't use current_msg_list as it won't work for muted messages or for out-of-narrow links
-    var message = message_store.get(target_id);
+    const message = message_store.get(target_id);
 
     // We don't check msg_list.can_mark_messages_read here only because
     // the target msg_list isn't initialized yet; in any case, the
@@ -644,21 +644,21 @@ exports.to_compose_target = function () {
         return;
     }
 
-    var opts = {
+    const opts = {
         trigger: 'narrow_to_compose_target',
     };
 
     if (compose_state.get_message_type() === 'stream') {
-        var stream_name = compose_state.stream_name();
-        var stream_id = stream_data.get_stream_id(stream_name);
+        const stream_name = compose_state.stream_name();
+        const stream_id = stream_data.get_stream_id(stream_name);
         if (!stream_id) {
             return;
         }
         // If we are composing to a new topic, we narrow to the stream but
         // grey-out the message view instead of narrowing to an empty view.
-        var topics = topic_data.get_recent_names(stream_id);
-        var operators = [{operator: 'stream', operand: stream_name}];
-        var topic = compose_state.topic();
+        const topics = topic_data.get_recent_names(stream_id);
+        const operators = [{operator: 'stream', operand: stream_name}];
+        const topic = compose_state.topic();
         if (topics.indexOf(topic) !== -1) {
             operators.push({operator: 'topic', operand: topic});
         }
@@ -667,9 +667,9 @@ exports.to_compose_target = function () {
     }
 
     if (compose_state.get_message_type() === 'private') {
-        var recipient_string = compose_state.recipient();
-        var emails = util.extract_pm_recipients(recipient_string);
-        var invalid = _.reject(emails, people.is_valid_email_for_compose);
+        const recipient_string = compose_state.recipient();
+        const emails = util.extract_pm_recipients(recipient_string);
+        const invalid = _.reject(emails, people.is_valid_email_for_compose);
         // If there are no recipients or any recipient is
         // invalid, narrow to all PMs.
         if (emails.length === 0 || invalid.length > 0) {
@@ -735,11 +735,11 @@ exports.deactivate = function () {
     hashchange.save_narrow();
 
     if (current_msg_list.selected_id() !== -1) {
-        var preserve_pre_narrowing_screen_position =
+        const preserve_pre_narrowing_screen_position =
             current_msg_list.selected_row().length > 0 &&
             current_msg_list.pre_narrow_offset !== undefined;
-        var message_id_to_select;
-        var select_opts = {
+        let message_id_to_select;
+        const select_opts = {
             then_scroll: true,
             use_closest: true,
             empty_ok: true,
@@ -790,27 +790,27 @@ exports.restore_home_state = function () {
 };
 
 function set_invalid_narrow_message(invalid_narrow_message) {
-    var search_string_display = $("#empty_search_stop_words_string");
+    const search_string_display = $("#empty_search_stop_words_string");
     search_string_display.text(invalid_narrow_message);
 }
 
 function show_search_query() {
     // when search bar contains multiple filters, only show search queries
-    var current_filter = narrow_state.filter();
-    var search_query = current_filter.operands("search")[0];
-    var query_words = search_query.split(" ");
+    const current_filter = narrow_state.filter();
+    const search_query = current_filter.operands("search")[0];
+    const query_words = search_query.split(" ");
 
-    var search_string_display = $("#empty_search_stop_words_string");
-    var query_contains_stop_words = false;
+    const search_string_display = $("#empty_search_stop_words_string");
+    let query_contains_stop_words = false;
 
     // Also removes previous search_string if any
     search_string_display.text(i18n.t("You searched for:"));
 
     // Add in stream:foo and topic:bar if present
     if (current_filter.has_operator("stream") || current_filter.has_operator("topic")) {
-        var stream_topic_string = "";
-        var stream = current_filter.operands('stream')[0];
-        var topic = current_filter.operands('topic')[0];
+        let stream_topic_string = "";
+        const stream = current_filter.operands('stream')[0];
+        const topic = current_filter.operands('topic')[0];
         if (stream) {
             stream_topic_string = "stream: " + stream;
         }
@@ -843,24 +843,24 @@ function show_search_query() {
 }
 
 function pick_empty_narrow_banner() {
-    var default_banner = $('#empty_narrow_message');
+    const default_banner = $('#empty_narrow_message');
 
-    var current_filter = narrow_state.filter();
+    const current_filter = narrow_state.filter();
 
     if (current_filter === undefined) {
         return default_banner;
     }
 
-    var first_term = current_filter.operators()[0];
-    var first_operator = first_term.operator;
-    var first_operand = first_term.operand;
-    var num_operators = current_filter.operators().length;
+    const first_term = current_filter.operators()[0];
+    const first_operator = first_term.operator;
+    const first_operand = first_term.operand;
+    const num_operators = current_filter.operators().length;
 
     if (num_operators !== 1) {
         // For invalid-multi-operator narrows, we display an invalid narrow message
-        var streams = current_filter.operands("stream");
+        const streams = current_filter.operands("stream");
 
-        var invalid_narrow_message = "";
+        let invalid_narrow_message = "";
         // No message can have multiple streams
         if (streams.length > 1) {
             invalid_narrow_message = i18n.t("You are searching for messages that belong to more than one stream, which is not possible.");
@@ -901,7 +901,7 @@ function pick_empty_narrow_banner() {
     } else if (first_operator === "stream" && !stream_data.is_subscribed(first_operand)) {
         // You are narrowed to a stream which does not exist or is a private stream
         // in which you were never subscribed.
-        var stream_sub = stream_data.get_sub(narrow_state.stream());
+        const stream_sub = stream_data.get_sub(narrow_state.stream());
         if (!stream_sub || !stream_sub.should_display_subscription_button) {
             return $("#nonsubbed_private_nonexistent_stream_narrow_message");
         }
diff --git a/static/js/popovers.js b/static/js/popovers.js
index f266f5ce4e..eb08f04d88 100644
--- a/static/js/popovers.js
+++ b/static/js/popovers.js
@@ -1,22 +1,22 @@
-var confirmDatePlugin = require("flatpickr/dist/plugins/confirmDate/confirmDate.js");
-var render_actions_popover_content = require('../templates/actions_popover_content.hbs');
-var render_mobile_message_buttons_popover = require('../templates/mobile_message_buttons_popover.hbs');
-var render_mobile_message_buttons_popover_content = require('../templates/mobile_message_buttons_popover_content.hbs');
-var render_no_arrow_popover = require('../templates/no_arrow_popover.hbs');
-var render_remind_me_popover_content = require('../templates/remind_me_popover_content.hbs');
-var render_user_group_info_popover = require('../templates/user_group_info_popover.hbs');
-var render_user_group_info_popover_content = require('../templates/user_group_info_popover_content.hbs');
-var render_user_info_popover_content = require('../templates/user_info_popover_content.hbs');
-var render_user_info_popover_title = require('../templates/user_info_popover_title.hbs');
-var render_user_profile_modal = require("../templates/user_profile_modal.hbs");
+const confirmDatePlugin = require("flatpickr/dist/plugins/confirmDate/confirmDate.js");
+const render_actions_popover_content = require('../templates/actions_popover_content.hbs');
+const render_mobile_message_buttons_popover = require('../templates/mobile_message_buttons_popover.hbs');
+const render_mobile_message_buttons_popover_content = require('../templates/mobile_message_buttons_popover_content.hbs');
+const render_no_arrow_popover = require('../templates/no_arrow_popover.hbs');
+const render_remind_me_popover_content = require('../templates/remind_me_popover_content.hbs');
+const render_user_group_info_popover = require('../templates/user_group_info_popover.hbs');
+const render_user_group_info_popover_content = require('../templates/user_group_info_popover_content.hbs');
+const render_user_info_popover_content = require('../templates/user_info_popover_content.hbs');
+const render_user_info_popover_title = require('../templates/user_info_popover_title.hbs');
+const render_user_profile_modal = require("../templates/user_profile_modal.hbs");
 
-var current_actions_popover_elem;
-var current_flatpickr_instance;
-var current_message_info_popover_elem;
-var current_mobile_message_buttons_popover_elem;
-var userlist_placement = "right";
+let current_actions_popover_elem;
+let current_flatpickr_instance;
+let current_message_info_popover_elem;
+let current_mobile_message_buttons_popover_elem;
+let userlist_placement = "right";
 
-var list_of_popovers = [];
+let list_of_popovers = [];
 
 // this utilizes the proxy pattern to intercept all calls to $.fn.popover
 // and push the $.fn.data($o, "popover") results to an array.
@@ -36,7 +36,7 @@ var list_of_popovers = [];
     };
 
     // add back all shallow properties of $.fn.popover to the new proxied version.
-    for (var x in popover) {
+    for (const x in popover) {
         if (popover.hasOwnProperty(x)) {
             $.fn.popover[x] = popover[x];
         }
@@ -44,12 +44,12 @@ var list_of_popovers = [];
 }($.fn.popover));
 
 function copy_email_handler(e) {
-    var email_el = $(e.trigger.parentElement);
-    var copy_icon = email_el.find('i');
+    const email_el = $(e.trigger.parentElement);
+    const copy_icon = email_el.find('i');
 
     // only change the parent element's text back to email
     // and not overwrite the tooltip.
-    var email_textnode = email_el[0].childNodes[2];
+    const email_textnode = email_el[0].childNodes[2];
 
     email_el.addClass('email_copied');
     email_textnode.nodeValue = i18n.t('Email copied');
@@ -64,19 +64,19 @@ function copy_email_handler(e) {
 function init_email_clipboard() {
     $('.user_popover_email').each(function () {
         if (this.clientWidth < this.scrollWidth) {
-            var email_el = $(this);
-            var copy_email_icon = email_el.find('i');
+            const email_el = $(this);
+            const copy_email_icon = email_el.find('i');
             copy_email_icon.removeClass('hide_copy_icon');
 
-            var copy_email_clipboard = new ClipboardJS(copy_email_icon[0]);
+            const copy_email_clipboard = new ClipboardJS(copy_email_icon[0]);
             copy_email_clipboard.on('success', copy_email_handler);
         }
     });
 }
 
 function load_medium_avatar(user, elt) {
-    var user_avatar_url = "avatar/" + user.user_id + "/medium";
-    var sender_avatar_medium = new Image();
+    const user_avatar_url = "avatar/" + user.user_id + "/medium";
+    const sender_avatar_medium = new Image();
     sender_avatar_medium.src = user_avatar_url;
     $(sender_avatar_medium).on("load", function () {
         elt.css("background-image", "url(" + $(this).attr("src") + ")");
@@ -84,7 +84,7 @@ function load_medium_avatar(user, elt) {
 }
 
 function calculate_info_popover_placement(size, elt) {
-    var ypos = elt.offset().top;
+    const ypos = elt.offset().top;
 
     if (!(ypos + size / 2 < message_viewport.height() &&
           ypos > size / 2)) {
@@ -97,9 +97,9 @@ function calculate_info_popover_placement(size, elt) {
 }
 
 function get_custom_profile_field_data(user, field, field_types, dateFormat) {
-    var field_value = people.get_custom_profile_data(user.user_id, field.id);
-    var field_type = field.type;
-    var profile_field = {};
+    const field_value = people.get_custom_profile_data(user.user_id, field.id);
+    const field_type = field.type;
+    const profile_field = {};
 
     if (!field_value) {
         return profile_field;
@@ -123,7 +123,7 @@ function get_custom_profile_field_data(user, field, field_types, dateFormat) {
         profile_field.value = field_value.value;
         break;
     case field_types.CHOICE.id: {
-        var field_choice_dict = JSON.parse(field.field_data);
+        const field_choice_dict = JSON.parse(field.field_data);
         profile_field.value = field_choice_dict[field_value.value].text;
         break;
     }
@@ -152,10 +152,10 @@ function get_visible_email(user) {
 
 function render_user_info_popover(user, popover_element, is_sender_popover, private_msg_class,
                                   template_class, popover_placement) {
-    var is_me = people.is_my_user_id(user.user_id);
+    const is_me = people.is_my_user_id(user.user_id);
 
-    var can_set_away = false;
-    var can_revoke_away = false;
+    let can_set_away = false;
+    let can_revoke_away = false;
 
     if (is_me) {
         if (user_status.is_away(user.user_id)) {
@@ -165,7 +165,7 @@ function render_user_info_popover(user, popover_element, is_sender_popover, priv
         }
     }
 
-    var args = {
+    const args = {
         can_revoke_away: can_revoke_away,
         can_set_away: can_set_away,
         is_active: people.is_active_user_for_popover(user.user_id),
@@ -188,12 +188,12 @@ function render_user_info_popover(user, popover_element, is_sender_popover, priv
     };
 
     if (user.is_bot) {
-        var is_cross_realm_bot = user.is_cross_realm_bot;
-        var bot_owner_id = user.bot_owner_id;
+        const is_cross_realm_bot = user.is_cross_realm_bot;
+        const bot_owner_id = user.bot_owner_id;
         if (is_cross_realm_bot) {
             args.is_cross_realm_bot = is_cross_realm_bot;
         } else if (bot_owner_id) {
-            var bot_owner = people.get_person_from_user_id(bot_owner_id);
+            const bot_owner = people.get_person_from_user_id(bot_owner_id);
             args.bot_owner = bot_owner;
         }
     }
@@ -228,7 +228,7 @@ exports._test_calculate_info_popover_placement = calculate_info_popover_placemen
 // user is the user whose profile to show
 // message is the message containing it, which should be selected
 function show_user_info_popover(element, user, message) {
-    var last_popover_elem = current_message_info_popover_elem;
+    const last_popover_elem = current_message_info_popover_elem;
     exports.hide_all();
     if (last_popover_elem !== undefined
         && last_popover_elem.get()[0] === element) {
@@ -237,7 +237,7 @@ function show_user_info_popover(element, user, message) {
         return;
     }
     current_msg_list.select_id(message.id);
-    var elt = $(element);
+    const elt = $(element);
     if (elt.data('popover') === undefined) {
         if (user === undefined) {
             // This is never supposed to happen, not even for deactivated
@@ -246,7 +246,7 @@ function show_user_info_popover(element, user, message) {
             return;
         }
 
-        var is_sender_popover =  message.sender_id === user.user_id;
+        const is_sender_popover =  message.sender_id === user.user_id;
         render_user_info_popover(user, elt, is_sender_popover, "respond_personal_button",
                                  "message-info-popover", "right");
 
@@ -255,7 +255,7 @@ function show_user_info_popover(element, user, message) {
 }
 
 function show_mobile_message_buttons_popover(element) {
-    var last_popover_elem = current_mobile_message_buttons_popover_elem;
+    const last_popover_elem = current_mobile_message_buttons_popover_elem;
     exports.hide_all();
     if (last_popover_elem !== undefined
         && last_popover_elem.get()[0] === element) {
@@ -264,7 +264,7 @@ function show_mobile_message_buttons_popover(element) {
         return;
     }
 
-    var $element = $(element);
+    const $element = $(element);
     $element.popover({
         placement: "left",
         template: render_mobile_message_buttons_popover(),
@@ -293,13 +293,13 @@ exports.hide_user_profile = function () {
 exports.show_user_profile = function (user) {
     exports.hide_all();
 
-    var dateFormat = moment.localeData().longDateFormat('LL');
-    var field_types = page_params.custom_profile_field_types;
-    var profile_data = page_params.custom_profile_fields
+    const dateFormat = moment.localeData().longDateFormat('LL');
+    const field_types = page_params.custom_profile_field_types;
+    const profile_data = page_params.custom_profile_fields
         .map(function (f) {return get_custom_profile_field_data(user, f, field_types, dateFormat);})
         .filter(function (f) {return f.name !== undefined;});
 
-    var args = {
+    const args = {
         full_name: user.full_name,
         email: get_visible_email(user),
         profile_data: profile_data,
@@ -325,7 +325,7 @@ function get_user_info_popover_items() {
         return;
     }
 
-    var popover_data = current_message_info_popover_elem.data('popover');
+    const popover_data = current_message_info_popover_elem.data('popover');
     if (!popover_data) {
         blueslip.error('Cannot find popover data for actions menu.');
         return;
@@ -366,10 +366,10 @@ exports._test_sort_group_members = sort_group_members;
 // user is the user whose profile to show
 // message is the message containing it, which should be selected
 function show_user_group_info_popover(element, group, message) {
-    var last_popover_elem = current_message_info_popover_elem;
+    const last_popover_elem = current_message_info_popover_elem;
     // hardcoded pixel height of the popover
     // note that the actual size varies (in group size), but this is about as big as it gets
-    var popover_size = 390;
+    const popover_size = 390;
     exports.hide_all();
     if (last_popover_elem !== undefined
         && last_popover_elem.get()[0] === element) {
@@ -378,9 +378,9 @@ function show_user_group_info_popover(element, group, message) {
         return;
     }
     current_msg_list.select_id(message.id);
-    var elt = $(element);
+    const elt = $(element);
     if (elt.data('popover') === undefined) {
-        var args = {
+        const args = {
             group_name: group.name,
             group_description: group.description,
             members: sort_group_members(fetch_group_members(group.members.keys())),
@@ -398,7 +398,7 @@ function show_user_group_info_popover(element, group, message) {
 }
 
 exports.toggle_actions_popover = function (element, id) {
-    var last_popover_elem = current_actions_popover_elem;
+    const last_popover_elem = current_actions_popover_elem;
     exports.hide_all();
     if (last_popover_elem !== undefined
         && last_popover_elem.get()[0] === element) {
@@ -409,12 +409,12 @@ exports.toggle_actions_popover = function (element, id) {
 
     $(element).closest('.message_row').toggleClass('has_popover has_actions_popover');
     current_msg_list.select_id(id);
-    var elt = $(element);
+    const elt = $(element);
     if (elt.data('popover') === undefined) {
-        var message = current_msg_list.get(id);
-        var editability = message_edit.get_editability(message);
-        var use_edit_icon;
-        var editability_menu_item;
+        const message = current_msg_list.get(id);
+        const editability = message_edit.get_editability(message);
+        let use_edit_icon;
+        let editability_menu_item;
         if (editability === message_edit.editability_types.FULL) {
             use_edit_icon = true;
             editability_menu_item = i18n.t("Edit");
@@ -425,43 +425,43 @@ exports.toggle_actions_popover = function (element, id) {
             use_edit_icon = false;
             editability_menu_item = i18n.t("View source");
         }
-        var topic = util.get_message_topic(message);
-        var can_mute_topic =
+        const topic = util.get_message_topic(message);
+        const can_mute_topic =
                 message.stream &&
                 topic &&
                 !muting.is_topic_muted(message.stream_id, topic);
-        var can_unmute_topic =
+        const can_unmute_topic =
                 message.stream &&
                 topic &&
                 muting.is_topic_muted(message.stream_id, topic);
 
-        var should_display_edit_history_option = _.any(message.edit_history, function (entry) {
-            var prev_topic = util.get_edit_event_prev_topic(entry);
+        const should_display_edit_history_option = _.any(message.edit_history, function (entry) {
+            const prev_topic = util.get_edit_event_prev_topic(entry);
             return entry.prev_content !== undefined || prev_topic !== undefined;
         }) && page_params.realm_allow_edit_history;
 
         // Disabling this for /me messages is a temporary workaround
         // for the fact that we don't have a styling for how that
         // should look.  See also condense.js.
-        var should_display_collapse = !message.locally_echoed &&
+        const should_display_collapse = !message.locally_echoed &&
                                       !message.is_me_message &&
                                       !message.collapsed;
-        var should_display_uncollapse = !message.locally_echoed &&
+        const should_display_uncollapse = !message.locally_echoed &&
                                         !message.is_me_message &&
                                         message.collapsed;
 
-        var should_display_edit_and_view_source =
+        const should_display_edit_and_view_source =
                 message.content !== '<p>(deleted)</p>' ||
                 editability === message_edit.editability_types.FULL ||
                 editability === message_edit.editability_types.TOPIC_ONLY;
-        var should_display_quote_and_reply = message.content !== '<p>(deleted)</p>';
+        const should_display_quote_and_reply = message.content !== '<p>(deleted)</p>';
 
-        var conversation_time_uri = hash_util.by_conversation_and_time_uri(message)
+        const conversation_time_uri = hash_util.by_conversation_and_time_uri(message)
             .replace(/\(/g, '%28')
             .replace(/\)/g, '%29');
 
-        var should_display_delete_option = message_edit.get_deletability(message);
-        var args = {
+        const should_display_delete_option = message_edit.get_deletability(message);
+        const args = {
             message_id: message.id,
             historical: message.historical,
             stream_id: message.stream_id,
@@ -482,7 +482,7 @@ exports.toggle_actions_popover = function (element, id) {
             should_display_quote_and_reply: should_display_quote_and_reply,
         };
 
-        var ypos = elt.offset().top;
+        const ypos = elt.offset().top;
         elt.popover({
             // Popover height with 7 items in it is ~190 px
             placement: message_viewport.height() - ypos < 220 ? 'top' : 'bottom',
@@ -500,13 +500,13 @@ exports.render_actions_remind_popover = function (element, id) {
     exports.hide_all();
     $(element).closest('.message_row').toggleClass('has_popover has_actions_popover');
     current_msg_list.select_id(id);
-    var elt = $(element);
+    const elt = $(element);
     if (elt.data('popover') === undefined) {
-        var message = current_msg_list.get(id);
-        var args = {
+        const message = current_msg_list.get(id);
+        const args = {
             message: message,
         };
-        var ypos = elt.offset().top;
+        const ypos = elt.offset().top;
         elt.popover({
             // Popover height with 7 items in it is ~190 px
             placement: message_viewport.height() - ypos < 220 ? 'top' : 'bottom',
@@ -533,7 +533,7 @@ function get_action_menu_menu_items() {
         return;
     }
 
-    var popover_data = current_actions_popover_elem.data('popover');
+    const popover_data = current_actions_popover_elem.data('popover');
     if (!popover_data) {
         blueslip.error('Cannot find popover data for actions menu.');
         return;
@@ -555,7 +555,7 @@ function popover_items_handle_keyboard(key, items) {
         return;
     }
 
-    var index = items.index(items.filter(':focus'));
+    let index = items.index(items.filter(':focus'));
 
     if (key === "enter" && index >= 0 && index < items.length) {
         return items[index].click();
@@ -573,7 +573,7 @@ function popover_items_handle_keyboard(key, items) {
 function focus_first_action_popover_item() {
     // For now I recommend only calling this when the user opens the menu with a hotkey.
     // Our popup menus act kind of funny when you mix keyboard and mouse.
-    var items = get_action_menu_menu_items();
+    const items = get_action_menu_menu_items();
     focus_first_popover_item(items);
 }
 
@@ -585,7 +585,7 @@ exports.open_message_menu = function (message) {
         return true;
     }
 
-    var id = message.id;
+    const id = message.id;
     exports.toggle_actions_popover($(".selected_message .actions_hover")[0], id);
     if (current_actions_popover_elem) {
         focus_first_action_popover_item();
@@ -594,7 +594,7 @@ exports.open_message_menu = function (message) {
 };
 
 exports.actions_menu_handle_keyboard = function (key) {
-    var items = get_action_menu_menu_items();
+    const items = get_action_menu_menu_items();
     popover_items_handle_keyboard(key, items);
 };
 
@@ -643,8 +643,8 @@ exports.show_pm_list_sidebar = function () {
     resize.resize_page_components();
 };
 
-var current_user_sidebar_user_id;
-var current_user_sidebar_popover;
+let current_user_sidebar_user_id;
+let current_user_sidebar_popover;
 
 function user_sidebar_popped() {
     return current_user_sidebar_popover !== undefined;
@@ -667,21 +667,21 @@ exports.hide_user_sidebar_popover = function () {
 function focus_user_info_popover_item() {
     // For now I recommend only calling this when the user opens the menu with a hotkey.
     // Our popup menus act kind of funny when you mix keyboard and mouse.
-    var items = get_user_info_popover_items();
+    const items = get_user_info_popover_items();
     focus_first_popover_item(items);
 }
 
 exports.user_info_popover_handle_keyboard = function (key) {
-    var items = get_user_info_popover_items();
+    const items = get_user_info_popover_items();
     popover_items_handle_keyboard(key, items);
 };
 
 exports.show_sender_info = function () {
-    var $message = $(".selected_message");
-    var $sender = $message.find('.sender_info_hover');
+    const $message = $(".selected_message");
+    const $sender = $message.find('.sender_info_hover');
 
-    var message = current_msg_list.get(rows.id($message));
-    var user = people.get_person_from_user_id(message.sender_id);
+    const message = current_msg_list.get(rows.id($message));
+    const user = people.get_person_from_user_id(message.sender_id);
     show_user_info_popover($sender[0], user, message);
     if (current_message_info_popover_elem) {
         focus_user_info_popover_item();
@@ -693,7 +693,7 @@ exports.show_sender_info = function () {
 // side effect of closing popovers, which we don't want.  So we
 // suppress the first hide from scrolling after a resize using this
 // variable.
-var suppress_scroll_hide = false;
+let suppress_scroll_hide = false;
 
 exports.set_suppress_scroll_hide = function () {
     suppress_scroll_hide = true;
@@ -701,32 +701,32 @@ exports.set_suppress_scroll_hide = function () {
 
 exports.register_click_handlers = function () {
     $("#main_div").on("click", ".actions_hover", function (e) {
-        var row = $(this).closest(".message_row");
+        const row = $(this).closest(".message_row");
         e.stopPropagation();
         exports.toggle_actions_popover(this, rows.id(row));
     });
 
     $("#main_div").on("click", ".sender_name, .sender_name-in-status, .inline_profile_picture", function (e) {
-        var row = $(this).closest(".message_row");
+        const row = $(this).closest(".message_row");
         e.stopPropagation();
-        var message = current_msg_list.get(rows.id(row));
-        var user = people.get_person_from_user_id(message.sender_id);
+        const message = current_msg_list.get(rows.id(row));
+        const user = people.get_person_from_user_id(message.sender_id);
 
         show_user_info_popover(this, user, message);
     });
 
     $("#main_div").on("click", ".user-mention", function (e) {
-        var id = $(this).attr('data-user-id');
+        const id = $(this).attr('data-user-id');
         // We fallback to email to handle legacy markdown that was rendered
         // before we cut over to using data-user-id
-        var email = $(this).attr('data-user-email');
+        const email = $(this).attr('data-user-email');
         if (id === '*' || email === '*') {
             return;
         }
-        var row = $(this).closest(".message_row");
+        const row = $(this).closest(".message_row");
         e.stopPropagation();
-        var message = current_msg_list.get(rows.id(row));
-        var user;
+        const message = current_msg_list.get(rows.id(row));
+        let user;
         if (id) {
             user = people.get_person_from_user_id(id);
         } else {
@@ -736,11 +736,11 @@ exports.register_click_handlers = function () {
     });
 
     $("#main_div").on("click", ".user-group-mention", function (e) {
-        var id = $(this).attr('data-user-group-id');
-        var row = $(this).closest(".message_row");
+        const id = $(this).attr('data-user-group-id');
+        const row = $(this).closest(".message_row");
         e.stopPropagation();
-        var message = current_msg_list.get(rows.id(row));
-        var group = user_groups.get_user_group_from_id(id, true);
+        const message = current_msg_list.get(rows.id(row));
+        const group = user_groups.get_user_group_from_id(id, true);
         if (group === undefined) {
             // This user group has likely been deleted.
             blueslip.info('Unable to find user group in message' + message.sender_id);
@@ -751,8 +751,8 @@ exports.register_click_handlers = function () {
 
 
     $('body').on('click', '.info_popover_actions .narrow_to_private_messages', function (e) {
-        var user_id = $(e.target).parents('ul').attr('data-user-id');
-        var email = people.get_person_from_user_id(user_id).email;
+        const user_id = $(e.target).parents('ul').attr('data-user-id');
+        const email = people.get_person_from_user_id(user_id).email;
         exports.hide_message_info_popover();
         narrow.by('pm-with', email, {trigger: 'user sidebar popover'});
         e.stopPropagation();
@@ -760,8 +760,8 @@ exports.register_click_handlers = function () {
     });
 
     $('body').on('click', '.info_popover_actions .narrow_to_messages_sent', function (e) {
-        var user_id = $(e.target).parents('ul').attr('data-user-id');
-        var email = people.get_person_from_user_id(user_id).email;
+        const user_id = $(e.target).parents('ul').attr('data-user-id');
+        const email = people.get_person_from_user_id(user_id).email;
         exports.hide_message_info_popover();
         narrow.by('sender', email, {trigger: 'user sidebar popover'});
         e.stopPropagation();
@@ -772,9 +772,9 @@ exports.register_click_handlers = function () {
         if (!compose_state.composing()) {
             compose_actions.start('stream', {trigger: 'sidebar user actions'});
         }
-        var user_id = $(e.target).parents('ul').attr('data-user-id');
-        var name = people.get_person_from_user_id(user_id).full_name;
-        var mention = people.get_mention_syntax(name, user_id);
+        const user_id = $(e.target).parents('ul').attr('data-user-id');
+        const name = people.get_person_from_user_id(user_id).full_name;
+        const mention = people.get_mention_syntax(name, user_id);
         compose_ui.insert_syntax_and_focus(mention);
         exports.hide_user_sidebar_popover();
         exports.hide_userlist_sidebar();
@@ -786,9 +786,9 @@ exports.register_click_handlers = function () {
         if (!compose_state.composing()) {
             compose_actions.respond_to_message({trigger: 'user sidebar popover'});
         }
-        var user_id = $(e.target).parents('ul').attr('data-user-id');
-        var name = people.get_person_from_user_id(user_id).full_name;
-        var mention = people.get_mention_syntax(name, user_id);
+        const user_id = $(e.target).parents('ul').attr('data-user-id');
+        const name = people.get_person_from_user_id(user_id).full_name;
+        const mention = people.get_mention_syntax(name, user_id);
         compose_ui.insert_syntax_and_focus(mention);
         exports.hide_message_info_popover();
         e.stopPropagation();
@@ -796,8 +796,8 @@ exports.register_click_handlers = function () {
     });
 
     $('body').on('click', '.info_popover_actions .view_user_profile', function (e) {
-        var user_id = $(e.target).parents('ul').attr('data-user-id');
-        var user = people.get_person_from_user_id(user_id);
+        const user_id = $(e.target).parents('ul').attr('data-user-id');
+        const user = people.get_person_from_user_id(user_id);
         exports.show_user_profile(user);
         e.stopPropagation();
         e.preventDefault();
@@ -805,7 +805,7 @@ exports.register_click_handlers = function () {
 
     $('body').on('click', '.info_popover_actions .clear_status', function (e) {
         e.preventDefault();
-        var me = $(e.target).parents('ul').attr('data-user-id');
+        const me = $(e.target).parents('ul').attr('data-user-id');
         user_status.server_update({
             user_id: me,
             status_text: '',
@@ -816,8 +816,8 @@ exports.register_click_handlers = function () {
     });
 
     $('body').on('click', '.bot-owner-name', function (e) {
-        var user_id = $(e.target).attr('data-bot-owner-id');
-        var user = people.get_person_from_user_id(user_id);
+        const user_id = $(e.target).attr('data-bot-owner-id');
+        const user = people.get_person_from_user_id(user_id);
         exports.show_user_profile(user);
     });
 
@@ -859,8 +859,8 @@ exports.register_click_handlers = function () {
 
         // use email of currently selected user, rather than some elem comparison,
         // as the presence list may be redrawn with new elements.
-        var target = $(this).closest('li');
-        var user_id = target.find('a').attr('data-user-id');
+        const target = $(this).closest('li');
+        const user_id = target.find('a').attr('data-user-id');
 
         if (String(current_user_sidebar_user_id) === user_id) {
             // If the popover is already shown, clicking again should toggle it.
@@ -877,8 +877,8 @@ exports.register_click_handlers = function () {
             stream_popover.show_streamlist_sidebar();
         }
 
-        var user = people.get_person_from_user_id(user_id);
-        var popover_placement = userlist_placement === "left" ? "right" : "left";
+        const user = people.get_person_from_user_id(user_id);
+        const popover_placement = userlist_placement === "left" ? "right" : "left";
 
         render_user_info_popover(user, target, false, "compose_private_message",
                                  "user_popover", popover_placement);
@@ -888,7 +888,7 @@ exports.register_click_handlers = function () {
     });
 
     $('body').on("mouseenter", ".user_popover_email", function () {
-        var tooltip_holder = $(this).find('div');
+        const tooltip_holder = $(this).find('div');
 
         if (this.offsetWidth < this.scrollWidth) {
             tooltip_holder.addClass('display-tooltip');
@@ -910,7 +910,7 @@ exports.register_click_handlers = function () {
     });
 
     $('body').on('click', '.reminder_button', function (e) {
-        var message_id = $(e.currentTarget).data('message-id');
+        const message_id = $(e.currentTarget).data('message-id');
         exports.render_actions_remind_popover($(".selected_message .actions_hover")[0], message_id);
         e.stopPropagation();
         e.preventDefault();
@@ -923,7 +923,7 @@ exports.register_click_handlers = function () {
     });
 
     function reminder_click_handler(datestr, e) {
-        var id = $(".remind.custom").data('message-id');
+        const id = $(".remind.custom").data('message-id');
         reminder.do_set_reminder_for_message(id, datestr);
         exports.hide_all();
         e.stopPropagation();
@@ -931,27 +931,27 @@ exports.register_click_handlers = function () {
     }
 
     $('body').on('click', '.remind.in_20m', function (e) {
-        var datestr = moment().add(20, 'm').format();
+        const datestr = moment().add(20, 'm').format();
         reminder_click_handler(datestr, e);
     });
 
     $('body').on('click', '.remind.in_1h', function (e) {
-        var datestr = moment().add(1, 'h').format();
+        const datestr = moment().add(1, 'h').format();
         reminder_click_handler(datestr, e);
     });
 
     $('body').on('click', '.remind.in_3h', function (e) {
-        var datestr = moment().add(3, 'h').format();
+        const datestr = moment().add(3, 'h').format();
         reminder_click_handler(datestr, e);
     });
 
     $('body').on('click', '.remind.tomo', function (e) {
-        var datestr = moment().add(1, 'd').hour(9).minute(0).seconds(0).format();
+        const datestr = moment().add(1, 'd').hour(9).minute(0).seconds(0).format();
         reminder_click_handler(datestr, e);
     });
 
     $('body').on('click', '.remind.nxtw', function (e) {
-        var datestr = moment().add(1, 'w').day('monday').hour(9).minute(0).seconds(0).format();
+        const datestr = moment().add(1, 'w').day('monday').hour(9).minute(0).seconds(0).format();
         reminder_click_handler(datestr, e);
     });
 
@@ -961,13 +961,13 @@ exports.register_click_handlers = function () {
     });
 
     $('body').on('click', '.flatpickr-confirm', function (e) {
-        var datestr = $(".remind.custom")[0].value;
+        const datestr = $(".remind.custom")[0].value;
         reminder_click_handler(datestr, e);
     });
 
     $('body').on('click', '.respond_personal_button, .compose_private_message', function (e) {
-        var user_id = $(e.target).parents('ul').attr('data-user-id');
-        var email = people.get_person_from_user_id(user_id).email;
+        const user_id = $(e.target).parents('ul').attr('data-user-id');
+        const email = people.get_person_from_user_id(user_id).email;
         compose_actions.start('private', {
             trigger: 'popover send private',
             private_message_recipient: email});
@@ -976,9 +976,9 @@ exports.register_click_handlers = function () {
         e.preventDefault();
     });
     $('body').on('click', '.popover_toggle_collapse', function (e) {
-        var message_id = $(e.currentTarget).data('message-id');
-        var row = current_msg_list.get_row(message_id);
-        var message = current_msg_list.get(rows.id(row));
+        const message_id = $(e.currentTarget).data('message-id');
+        const row = current_msg_list.get_row(message_id);
+        const message = current_msg_list.get(rows.id(row));
 
         exports.hide_actions_popover();
 
@@ -994,18 +994,18 @@ exports.register_click_handlers = function () {
         e.preventDefault();
     });
     $('body').on('click', '.popover_edit_message', function (e) {
-        var message_id = $(e.currentTarget).data('message-id');
-        var row = current_msg_list.get_row(message_id);
+        const message_id = $(e.currentTarget).data('message-id');
+        const row = current_msg_list.get_row(message_id);
         exports.hide_actions_popover();
         message_edit.start(row);
         e.stopPropagation();
         e.preventDefault();
     });
     $('body').on('click', '.view_edit_history', function (e) {
-        var message_id = $(e.currentTarget).data('message-id');
-        var row = current_msg_list.get_row(message_id);
-        var message = current_msg_list.get(rows.id(row));
-        var message_history_cancel_btn = $('#message-history-cancel');
+        const message_id = $(e.currentTarget).data('message-id');
+        const row = current_msg_list.get_row(message_id);
+        const message = current_msg_list.get(rows.id(row));
+        const message_history_cancel_btn = $('#message-history-cancel');
 
         exports.hide_actions_popover();
         message_edit.show_history(message);
@@ -1015,8 +1015,8 @@ exports.register_click_handlers = function () {
     });
 
     $('body').on('click', '.popover_mute_topic', function (e) {
-        var stream_id = $(e.currentTarget).attr('data-msg-stream-id');
-        var topic = $(e.currentTarget).attr('data-msg-topic');
+        const stream_id = $(e.currentTarget).attr('data-msg-stream-id');
+        const topic = $(e.currentTarget).attr('data-msg-topic');
 
         exports.hide_actions_popover();
         muting_ui.mute(stream_id, topic);
@@ -1025,8 +1025,8 @@ exports.register_click_handlers = function () {
     });
 
     $('body').on('click', '.popover_unmute_topic', function (e) {
-        var stream_id = $(e.currentTarget).attr('data-msg-stream-id');
-        var topic = $(e.currentTarget).attr('data-msg-topic');
+        const stream_id = $(e.currentTarget).attr('data-msg-stream-id');
+        const topic = $(e.currentTarget).attr('data-msg-topic');
 
         exports.hide_actions_popover();
         muting_ui.unmute(stream_id, topic);
@@ -1035,7 +1035,7 @@ exports.register_click_handlers = function () {
     });
 
     $('body').on('click', '.delete_message', function (e) {
-        var message_id = $(e.currentTarget).data('message-id');
+        const message_id = $(e.currentTarget).data('message-id');
         exports.hide_actions_popover();
         message_edit.delete_message(message_id);
         e.stopPropagation();
@@ -1046,8 +1046,8 @@ exports.register_click_handlers = function () {
 
     $('body').on('click', '.copy_link', function (e) {
         exports.hide_actions_popover();
-        var id = $(this).attr("data-message-id");
-        var row = $("[zid='" + id + "']");
+        const id = $(this).attr("data-message-id");
+        const row = $("[zid='" + id + "']");
         row.find(".alert-msg")
             .text(i18n.t("Copied!"))
             .css("display", "block")
@@ -1064,7 +1064,7 @@ exports.register_click_handlers = function () {
     });
 
     (function () {
-        var last_scroll = 0;
+        let last_scroll = 0;
 
         $('.app').on('scroll', function () {
             if (suppress_scroll_hide) {
@@ -1072,7 +1072,7 @@ exports.register_click_handlers = function () {
                 return;
             }
 
-            var date = new Date().getTime();
+            const date = new Date().getTime();
 
             // only run `popovers.hide_all()` if the last scroll was more
             // than 250ms ago.
@@ -1135,22 +1135,22 @@ exports.set_userlist_placement = function (placement) {
 
 exports.compute_placement = function (elt, popover_height, popover_width,
                                       prefer_vertical_positioning) {
-    var client_rect = elt.get(0).getBoundingClientRect();
-    var distance_from_top = client_rect.top;
-    var distance_from_bottom = message_viewport.height() - client_rect.bottom;
-    var distance_from_left = client_rect.left;
-    var distance_from_right = message_viewport.width() - client_rect.right;
+    const client_rect = elt.get(0).getBoundingClientRect();
+    const distance_from_top = client_rect.top;
+    const distance_from_bottom = message_viewport.height() - client_rect.bottom;
+    const distance_from_left = client_rect.left;
+    const distance_from_right = message_viewport.width() - client_rect.right;
 
-    var elt_will_fit_horizontally =
+    const elt_will_fit_horizontally =
         distance_from_left + elt.width() / 2 > popover_width / 2 &&
         distance_from_right + elt.width() / 2 > popover_width / 2;
 
-    var elt_will_fit_vertically =
+    const elt_will_fit_vertically =
         distance_from_bottom + elt.height() / 2 > popover_height / 2 &&
         distance_from_top + elt.height() / 2 > popover_height / 2;
 
     // default to placing the popover in the center of the screen
-    var placement = 'viewport_center';
+    let placement = 'viewport_center';
 
     // prioritize left/right over top/bottom
     if (distance_from_top > popover_height && elt_will_fit_horizontally) {
diff --git a/static/js/settings_org.js b/static/js/settings_org.js
index 750539f0f6..fb96611b6b 100644
--- a/static/js/settings_org.js
+++ b/static/js/settings_org.js
@@ -216,7 +216,7 @@ function set_invite_to_stream_policy_dropdown() {
 }
 
 function set_user_group_edit_policy_dropdown() {
-    var value = get_property_value("realm_user_group_edit_policy");
+    const value = get_property_value("realm_user_group_edit_policy");
     $("#id_realm_user_group_edit_policy").val(value);
 }
 
@@ -839,7 +839,7 @@ exports.build_page = function () {
             data = {};
             data.authentication_methods = JSON.stringify(get_auth_method_table_data());
         } else if (subsection === 'user_defaults') {
-            var realm_default_twenty_four_hour_time = $('#id_realm_default_twenty_four_hour_time').val();
+            const realm_default_twenty_four_hour_time = $('#id_realm_default_twenty_four_hour_time').val();
             data.default_twenty_four_hour_time = realm_default_twenty_four_hour_time;
         }
         return data;
diff --git a/static/js/settings_user_groups.js b/static/js/settings_user_groups.js
index f377bbc98c..d0f0bf5f69 100644
--- a/static/js/settings_user_groups.js
+++ b/static/js/settings_user_groups.js
@@ -1,7 +1,7 @@
-var render_admin_user_group_list = require('../templates/admin_user_group_list.hbs');
-var render_confirm_delete_user = require('../templates/confirm_delete_user.hbs');
+const render_admin_user_group_list = require('../templates/admin_user_group_list.hbs');
+const render_confirm_delete_user = require('../templates/confirm_delete_user.hbs');
 
-var meta = {
+const meta = {
     loaded: false,
 };
 
@@ -14,7 +14,7 @@ exports.reload = function () {
         return;
     }
 
-    var user_groups_section = $('#user-groups').expectOne();
+    const user_groups_section = $('#user-groups').expectOne();
     user_groups_section.html('');
     exports.populate_user_groups();
 };
@@ -39,8 +39,8 @@ exports.can_edit = function (group_id) {
 
 exports.populate_user_groups = function () {
 
-    var user_groups_section = $('#user-groups').expectOne();
-    var user_groups_array = user_groups.get_realm_user_groups();
+    const user_groups_section = $('#user-groups').expectOne();
+    const user_groups_array = user_groups.get_realm_user_groups();
     _.each(user_groups_array, function (data) {
         user_groups_section.append(render_admin_user_group_list({
             user_group: {
@@ -49,16 +49,16 @@ exports.populate_user_groups = function () {
                 description: data.description,
             },
         }));
-        var pill_container = $('.pill-container[data-group-pills="' + data.id + '"]');
-        var pills = user_pill.create_pills(pill_container);
+        const pill_container = $('.pill-container[data-group-pills="' + data.id + '"]');
+        const pills = user_pill.create_pills(pill_container);
 
         function get_pill_user_ids() {
             return user_pill.get_user_ids(pills);
         }
 
-        var userg = $('div.user-group[id="' + data.id + '"]');
+        const userg = $('div.user-group[id="' + data.id + '"]');
         data.members.keys().forEach(function (user_id) {
-            var user = people.get_person_from_user_id(user_id);
+            const user = people.get_person_from_user_id(user_id);
             user_pill.append_user(user, pills);
         });
 
@@ -85,13 +85,13 @@ exports.populate_user_groups = function () {
         update_membership(data.id);
 
         function is_user_group_changed() {
-            var draft_group = get_pill_user_ids();
-            var group_data = user_groups.get_user_group_from_id(data.id);
-            var original_group = group_data.members.keys();
-            var same_groups = _.isEqual(_.sortBy(draft_group), _.sortBy(original_group));
-            var description = $('#user-groups #' + data.id + ' .description').text().trim();
-            var name = $('#user-groups #' + data.id + ' .name').text().trim();
-            var user_group_status = $('#user-groups #' + data.id + ' .user-group-status');
+            const draft_group = get_pill_user_ids();
+            const group_data = user_groups.get_user_group_from_id(data.id);
+            const original_group = group_data.members.keys();
+            const same_groups = _.isEqual(_.sortBy(draft_group), _.sortBy(original_group));
+            const description = $('#user-groups #' + data.id + ' .description').text().trim();
+            const name = $('#user-groups #' + data.id + ' .name').text().trim();
+            const user_group_status = $('#user-groups #' + data.id + ' .user-group-status');
 
             if (user_group_status.is(':visible')) {
                 return false;
@@ -108,9 +108,9 @@ exports.populate_user_groups = function () {
             if (!exports.can_edit(data.id)) {
                 return;
             }
-            var cancel_button = $('#user-groups #' + data.id + ' .save-status.btn-danger');
-            var saved_button = $('#user-groups #' + data.id + ' .save-status.sea-green');
-            var save_instructions = $('#user-groups #' + data.id + ' .save-instructions');
+            const cancel_button = $('#user-groups #' + data.id + ' .save-status.btn-danger');
+            const saved_button = $('#user-groups #' + data.id + ' .save-status.sea-green');
+            const save_instructions = $('#user-groups #' + data.id + ' .save-instructions');
 
             if (is_user_group_changed() &&
                !cancel_button.is(':visible')) {
@@ -125,9 +125,9 @@ exports.populate_user_groups = function () {
         }
 
         function show_saved_button() {
-            var cancel_button = $('#user-groups #' + data.id + ' .save-status.btn-danger');
-            var saved_button = $('#user-groups #' + data.id + ' .save-status.sea-green');
-            var save_instructions = $('#user-groups #' + data.id + ' .save-instructions');
+            const cancel_button = $('#user-groups #' + data.id + ' .save-status.btn-danger');
+            const saved_button = $('#user-groups #' + data.id + ' .save-status.sea-green');
+            const save_instructions = $('#user-groups #' + data.id + ' .save-instructions');
             if (!saved_button.is(':visible')) {
                 cancel_button.fadeOut(0);
                 save_instructions.fadeOut(0);
@@ -136,15 +136,15 @@ exports.populate_user_groups = function () {
         }
 
         function save_members() {
-            var draft_group = get_pill_user_ids();
-            var group_data = user_groups.get_user_group_from_id(data.id);
-            var original_group = group_data.members.keys();
-            var same_groups = _.isEqual(_.sortBy(draft_group), _.sortBy(original_group));
+            const draft_group = get_pill_user_ids();
+            const group_data = user_groups.get_user_group_from_id(data.id);
+            const original_group = group_data.members.keys();
+            const same_groups = _.isEqual(_.sortBy(draft_group), _.sortBy(original_group));
             if (!draft_group.length || same_groups) {
                 return;
             }
-            var added = _.difference(draft_group, original_group);
-            var removed = _.difference(original_group, draft_group);
+            const added = _.difference(draft_group, original_group);
+            const removed = _.difference(original_group, draft_group);
             channel.post({
                 url: "/json/user_groups/" + data.id + '/members',
                 data: {
@@ -158,10 +158,10 @@ exports.populate_user_groups = function () {
         }
 
         function save_name_desc() {
-            var user_group_status = $('#user-groups #' + data.id + ' .user-group-status');
-            var group_data = user_groups.get_user_group_from_id(data.id);
-            var description = $('#user-groups #' + data.id + ' .description').text().trim();
-            var name = $('#user-groups #' + data.id + ' .name').text().trim();
+            const user_group_status = $('#user-groups #' + data.id + ' .user-group-status');
+            const group_data = user_groups.get_user_group_from_id(data.id);
+            const description = $('#user-groups #' + data.id + ' .description').text().trim();
+            const name = $('#user-groups #' + data.id + ' .name').text().trim();
 
             if (group_data.description === description && group_data.name === name) {
                 return;
@@ -178,7 +178,7 @@ exports.populate_user_groups = function () {
                     setTimeout(show_saved_button, 200);
                 },
                 error: function (xhr) {
-                    var errors = JSON.parse(xhr.responseText).msg;
+                    const errors = JSON.parse(xhr.responseText).msg;
                     xhr.responseText = JSON.stringify({msg: errors});
                     ui_report.error(i18n.t("Failed"), xhr, user_group_status);
                     update_cancel_button();
@@ -194,8 +194,8 @@ exports.populate_user_groups = function () {
                 return true;
             }
 
-            var blur_exceptions = _.without([".pill-container", ".name", ".description", ".input", ".delete"],
-                                            except_class);
+            const blur_exceptions = _.without([".pill-container", ".name", ".description", ".input", ".delete"],
+                                              except_class);
             if ($(event.relatedTarget).closest('#user-groups #' + data.id).length) {
                 return _.some(blur_exceptions, function (class_name) {
                     return $(event.relatedTarget).closest(class_name).length;
@@ -239,7 +239,7 @@ exports.populate_user_groups = function () {
             update_cancel_button();
         });
 
-        var input = pill_container.children('.input');
+        const input = pill_container.children('.input');
         if (exports.can_edit(data.id)) {
             user_pill.set_up_typeahead_on_pills(input, pills, update_cancel_button);
         }
@@ -268,9 +268,9 @@ exports.set_up = function () {
         e.preventDefault();
         e.stopPropagation();
 
-        var user_group_status = $('#admin-user-group-status');
+        const user_group_status = $('#admin-user-group-status');
 
-        var group = {
+        const group = {
             members: JSON.stringify([people.my_current_user_id()]),
         };
         _.each($(this).serializeArray(), function (obj) {
@@ -290,7 +290,7 @@ exports.set_up = function () {
             },
             error: function (xhr) {
                 user_group_status.hide();
-                var errors = JSON.parse(xhr.responseText).msg;
+                const errors = JSON.parse(xhr.responseText).msg;
                 xhr.responseText = JSON.stringify({msg: errors});
                 ui_report.error(i18n.t("Failed"), xhr, user_group_status);
             },
@@ -298,12 +298,12 @@ exports.set_up = function () {
     });
 
     $('#user-groups').on('click', '.delete', function () {
-        var group_id = $(this).parents('.user-group').attr('id');
+        const group_id = $(this).parents('.user-group').attr('id');
         if (!exports.can_edit(group_id)) {
             return;
         }
-        var user_group = user_groups.get_user_group_from_id(group_id);
-        var btn = $(this);
+        const user_group = user_groups.get_user_group_from_id(group_id);
+        const btn = $(this);
 
         function delete_user_group() {
             channel.del({
@@ -322,9 +322,9 @@ exports.set_up = function () {
         }
 
         // This is mostly important for styling concerns.
-        var modal_parent = $('#settings_content');
+        const modal_parent = $('#settings_content');
 
-        var html_body = render_confirm_delete_user({
+        const html_body = render_confirm_delete_user({
             group_name: user_group.name,
         });
 
diff --git a/static/js/stream_create.js b/static/js/stream_create.js
index 1450e3d65b..ab6afe7882 100644
--- a/static/js/stream_create.js
+++ b/static/js/stream_create.js
@@ -1,8 +1,8 @@
-var render_announce_stream_docs = require('../templates/announce_stream_docs.hbs');
-var render_new_stream_users = require('../templates/new_stream_users.hbs');
-var render_subscription_invites_warning_modal = require('../templates/subscription_invites_warning_modal.hbs');
+const render_announce_stream_docs = require('../templates/announce_stream_docs.hbs');
+const render_new_stream_users = require('../templates/new_stream_users.hbs');
+const render_subscription_invites_warning_modal = require('../templates/subscription_invites_warning_modal.hbs');
 
-var created_stream;
+let created_stream;
 
 exports.reset_created_stream = function () {
     created_stream = undefined;
@@ -16,8 +16,8 @@ exports.get_name = function () {
     return created_stream;
 };
 
-var stream_subscription_error = (function () {
-    var self = {};
+const stream_subscription_error = (function () {
+    const self = {};
 
     self.report_no_subs_to_stream = function () {
         $("#stream_subscription_error").text(i18n.t("You cannot create a stream with no subscribers!"));
@@ -37,8 +37,8 @@ var stream_subscription_error = (function () {
 
 }());
 
-var stream_name_error = (function () {
-    var self = {};
+const stream_name_error = (function () {
+    const self = {};
 
     self.report_already_exists = function () {
         $("#stream_name_error").text(i18n.t("A stream with this name already exists"));
@@ -118,7 +118,7 @@ function ajaxSubscribeForCreation(stream_name, description, principals, invite_o
             // The rest of the work is done via the subscribe event we will get
         },
         error: function (xhr) {
-            var msg = JSON.parse(xhr.responseText).msg;
+            const msg = JSON.parse(xhr.responseText).msg;
             if (msg.indexOf('access') >= 0) {
                 // If we can't access the stream, we can safely assume it's
                 // a duplicate stream that we are not invited to.
@@ -143,11 +143,11 @@ function update_announce_stream_state() {
 
     // If the stream is invite only, disable the "Announce stream" option.
     // Otherwise enable it.
-    var announce_stream_checkbox = $('#announce-new-stream input');
-    var announce_stream_label = $('#announce-new-stream');
-    var disable_it = false;
-    var privacy_type = $('input:radio[name=privacy]:checked').val();
-    var is_invite_only = privacy_type === "invite-only" || privacy_type === "invite-only-public-history";
+    const announce_stream_checkbox = $('#announce-new-stream input');
+    const announce_stream_label = $('#announce-new-stream');
+    let disable_it = false;
+    const privacy_type = $('input:radio[name=privacy]:checked').val();
+    const is_invite_only = privacy_type === "invite-only" || privacy_type === "invite-only-public-history";
     announce_stream_label.removeClass("control-label-disabled");
 
     if (is_invite_only) {
@@ -170,14 +170,14 @@ function get_principals() {
 }
 
 function create_stream() {
-    var stream_name = $.trim($("#create_stream_name").val());
-    var description = $.trim($("#create_stream_description").val());
-    var privacy_setting = $('#stream_creation_form input[name=privacy]:checked').val();
-    var is_announcement_only = $('#stream_creation_form input[name=is-announcement-only]').prop('checked');
-    var principals = get_principals();
+    const stream_name = $.trim($("#create_stream_name").val());
+    const description = $.trim($("#create_stream_description").val());
+    const privacy_setting = $('#stream_creation_form input[name=privacy]:checked').val();
+    const is_announcement_only = $('#stream_creation_form input[name=is-announcement-only]').prop('checked');
+    const principals = get_principals();
 
-    var invite_only;
-    var history_public_to_subscribers;
+    let invite_only;
+    let history_public_to_subscribers;
 
     if (privacy_setting === 'invite-only') {
         invite_only = true;
@@ -192,7 +192,7 @@ function create_stream() {
 
     created_stream = stream_name;
 
-    var announce = !!page_params.notifications_stream &&
+    const announce = !!page_params.notifications_stream &&
         $('#announce-new-stream input').prop('checked');
 
     // Even though we already check to make sure that while typing the user cannot enter
@@ -254,16 +254,16 @@ exports.show_new_stream_modal = function () {
     $("#stream-creation").removeClass("hide");
     $(".right .settings").hide();
 
-    var all_users = people.get_rest_of_realm();
+    const all_users = people.get_rest_of_realm();
     // Add current user on top of list
     all_users.unshift(people.get_person_from_user_id(page_params.user_id));
-    var html = render_new_stream_users({
+    const html = render_new_stream_users({
         users: all_users,
         streams: stream_data.get_streams_for_settings_page(),
         is_admin: page_params.is_admin,
     });
 
-    var container = $('#people_to_add');
+    const container = $('#people_to_add');
     container.html(html);
     exports.create_handlers_for_users(container);
 
@@ -281,14 +281,14 @@ exports.show_new_stream_modal = function () {
     clear_error_display();
 
     $("#stream-checkboxes label.checkbox").on('change', function (e) {
-        var elem = $(this);
-        var stream_id = elem.attr('data-stream-id');
-        var checked = elem.find('input').prop('checked');
-        var subscriber_ids = stream_data.get_sub_by_id(stream_id).subscribers;
+        const elem = $(this);
+        const stream_id = elem.attr('data-stream-id');
+        const checked = elem.find('input').prop('checked');
+        const subscriber_ids = stream_data.get_sub_by_id(stream_id).subscribers;
 
         $('#user-checkboxes label.checkbox').each(function () {
-            var user_elem = $(this);
-            var user_id = user_elem.attr('data-user-id');
+            const user_elem = $(this);
+            const user_id = user_elem.attr('data-user-id');
 
             if (subscriber_ids.has(user_id)) {
                 user_elem.find('input').prop('checked', checked);
@@ -337,23 +337,23 @@ exports.create_handlers_for_users = function (container) {
 
     // Search People or Streams
     container.on('input', '.add-user-list-filter', function (e) {
-        var user_list = $(".add-user-list-filter");
+        const user_list = $(".add-user-list-filter");
         if (user_list === 0) {
             return;
         }
-        var search_term = user_list.expectOne().val().trim();
-        var search_terms = search_term.toLowerCase().split(",");
+        const search_term = user_list.expectOne().val().trim();
+        const search_terms = search_term.toLowerCase().split(",");
 
         (function filter_user_checkboxes() {
-            var user_labels = $("#user-checkboxes label.add-user-label");
+            const user_labels = $("#user-checkboxes label.add-user-label");
 
             if (search_term === '') {
                 user_labels.css({display: 'block'});
                 return;
             }
 
-            var users = people.get_rest_of_realm();
-            var filtered_users = people.filter_people_by_search_terms(users, search_terms);
+            const users = people.get_rest_of_realm();
+            const filtered_users = people.filter_people_by_search_terms(users, search_terms);
 
             // Be careful about modifying the follow code.  A naive implementation
             // will work very poorly with a large user population (~1000 users).
@@ -363,10 +363,10 @@ exports.create_handlers_for_users = function (container) {
             // This would break the previous implementation, whereas the new
             // implementation is merely sluggish.
             user_labels.each(function () {
-                var elem = $(this);
-                var user_id = elem.attr('data-user-id');
-                var user_checked = filtered_users.has(user_id);
-                var display = user_checked ? "block" : "none";
+                const elem = $(this);
+                const user_id = elem.attr('data-user-id');
+                const user_checked = filtered_users.has(user_id);
+                const display = user_checked ? "block" : "none";
                 elem.css({display: display});
             });
         }());
@@ -377,7 +377,7 @@ exports.create_handlers_for_users = function (container) {
 
 
 exports.set_up_handlers = function () {
-    var container = $('#stream-creation').expectOne();
+    const container = $('#stream-creation').expectOne();
 
     container.on('change', '#make-invite-only input', update_announce_stream_state);
 
@@ -385,14 +385,14 @@ exports.set_up_handlers = function () {
         e.preventDefault();
         clear_error_display();
 
-        var stream_name = $.trim($("#create_stream_name").val());
-        var name_ok = stream_name_error.validate_for_submit(stream_name);
+        const stream_name = $.trim($("#create_stream_name").val());
+        const name_ok = stream_name_error.validate_for_submit(stream_name);
 
         if (!name_ok) {
             return;
         }
 
-        var principals = get_principals();
+        const principals = get_principals();
         if (principals.length === 0) {
             stream_subscription_error.report_no_subs_to_stream();
             return;
@@ -403,7 +403,7 @@ exports.set_up_handlers = function () {
         }
 
         if (principals.length >= 50) {
-            var invites_warning_modal = render_subscription_invites_warning_modal({
+            const invites_warning_modal = render_subscription_invites_warning_modal({
                 stream_name: stream_name,
                 count: principals.length,
             });
@@ -423,14 +423,14 @@ exports.set_up_handlers = function () {
     });
 
     container.on("input", "#create_stream_name", function () {
-        var stream_name = $.trim($("#create_stream_name").val());
+        const stream_name = $.trim($("#create_stream_name").val());
 
         // This is an inexpensive check.
         stream_name_error.pre_validate(stream_name);
     });
 
     container.on("mouseover", "#announce-stream-docs", function (e) {
-        var announce_stream_docs = $("#announce-stream-docs");
+        const announce_stream_docs = $("#announce-stream-docs");
         announce_stream_docs.popover({
             placement: "right",
             content: render_announce_stream_docs({
diff --git a/static/js/subs.js b/static/js/subs.js
index 1945b5412c..1a03e8372f 100644
--- a/static/js/subs.js
+++ b/static/js/subs.js
@@ -1,7 +1,7 @@
-var render_subscription = require('../templates/subscription.hbs');
-var render_subscription_settings = require('../templates/subscription_settings.hbs');
-var render_subscription_table_body = require('../templates/subscription_table_body.hbs');
-var render_subscriptions = require('../templates/subscriptions.hbs');
+const render_subscription = require('../templates/subscription.hbs');
+const render_subscription_settings = require('../templates/subscription_settings.hbs');
+const render_subscription_table_body = require('../templates/subscription_table_body.hbs');
+const render_subscriptions = require('../templates/subscriptions.hbs');
 
 exports.show_subs_pane = {
     nothing_selected: function () {
@@ -15,7 +15,7 @@ exports.show_subs_pane = {
 };
 
 exports.check_button_for_sub = function (sub) {
-    var id = parseInt(sub.stream_id, 10);
+    const id = parseInt(sub.stream_id, 10);
     return $(".stream-row[data-stream-id='" + id + "'] .check");
 };
 
@@ -26,14 +26,14 @@ exports.row_for_stream_id = function (stream_id) {
 exports.settings_button_for_sub = function (sub) {
     // We don't do expectOne() here, because this button is only
     // visible if the user has that stream selected in the streams UI.
-    var id = parseInt(sub.stream_id, 10);
+    const id = parseInt(sub.stream_id, 10);
     return $(".subscription_settings[data-stream-id='" + id + "'] .subscribe-button");
 };
 
 function get_row_data(row) {
-    var row_id = row.attr('data-stream-id');
+    const row_id = row.attr('data-stream-id');
     if (row_id) {
-        var row_object = stream_data.get_sub_by_id(row_id);
+        const row_object = stream_data.get_sub_by_id(row_id);
         return {
             id: row_id,
             object: row_object,
@@ -42,9 +42,9 @@ function get_row_data(row) {
 }
 
 exports.get_active_data = function () {
-    var active_row = $('div.stream-row.active');
-    var valid_active_id = active_row.attr('data-stream-id');
-    var active_tab = $('.subscriptions-container').find('div.ind-tab.selected');
+    const active_row = $('div.stream-row.active');
+    const valid_active_id = active_row.attr('data-stream-id');
+    const active_tab = $('.subscriptions-container').find('div.ind-tab.selected');
     return {
         row: active_row,
         id: valid_active_id,
@@ -61,8 +61,8 @@ function get_hash_safe() {
 }
 
 function selectText(element) {
-    var range;
-    var sel;
+    let range;
+    let sel;
     if (window.getSelection) {
         sel = window.getSelection();
         range = document.createRange();
@@ -84,7 +84,7 @@ function should_list_all_streams() {
 // this finds the stream that is actively open in the settings and focused in
 // the left side.
 exports.active_stream = function () {
-    var hash_components = window.location.hash.substr(1).split(/\//);
+    const hash_components = window.location.hash.substr(1).split(/\//);
 
     // if the string casted to a number is valid, and another component
     // after exists then it's a stream name/id pair.
@@ -106,7 +106,7 @@ exports.toggle_pin_to_top_stream = function (sub) {
 };
 
 exports.maybe_update_realm_default_stream_name  = function (stream_id, new_name) {
-    var idx = _.findIndex(page_params.realm_default_streams, function (stream) {
+    const idx = _.findIndex(page_params.realm_default_streams, function (stream) {
         return stream.stream_id === stream_id;
     });
     if (idx === -1) {
@@ -125,11 +125,11 @@ exports.is_subscribed_stream_tab_active = function () {
 };
 
 exports.update_stream_name = function (sub, new_name) {
-    var old_name = sub.name;
+    const old_name = sub.name;
 
     // Rename the stream internally.
     stream_data.rename_sub(sub, new_name);
-    var stream_id = sub.stream_id;
+    const stream_id = sub.stream_id;
 
     // Update the left sidebar.
     stream_list.rename_stream(sub, new_name);
@@ -141,7 +141,7 @@ exports.update_stream_name = function (sub, new_name) {
     stream_edit.update_stream_name(sub, new_name);
 
     // Update the subscriptions page
-    var sub_row = exports.row_for_stream_id(stream_id);
+    const sub_row = exports.row_for_stream_id(stream_id);
     sub_row.find(".stream-name").text(new_name);
 
     // Update the message feed.
@@ -161,7 +161,7 @@ exports.update_stream_description = function (sub, description, rendered_descrip
     sub.rendered_description = rendered_description.replace('<p>', '').replace('</p>', '');
 
     // Update stream row
-    var sub_row = exports.row_for_stream_id(sub.stream_id);
+    const sub_row = exports.row_for_stream_id(sub.stream_id);
     sub_row.find(".description").html(sub.rendered_description);
 
     // Update stream settings
@@ -190,7 +190,7 @@ exports.update_stream_announcement_only = function (sub, new_value) {
 };
 
 exports.set_color = function (stream_id, color) {
-    var sub = stream_data.get_sub_by_id(stream_id);
+    const sub = stream_data.get_sub_by_id(stream_id);
     stream_edit.set_stream_property(sub, 'color', color);
 };
 
@@ -218,8 +218,8 @@ exports.add_sub_to_table = function (sub) {
         return;
     }
 
-    var html = render_subscription(sub);
-    var settings_html = render_subscription_settings(sub);
+    const html = render_subscription(sub);
+    const settings_html = render_subscription_settings(sub);
     if (stream_create.get_name() === sub.name) {
         ui.get_content_element($(".streams-list")).prepend(html);
         ui.reset_scrollbar($(".streams-list"));
@@ -243,7 +243,7 @@ exports.add_sub_to_table = function (sub) {
 exports.is_sub_already_present = function (sub) {
     // This checks if a stream is already listed the "Manage streams"
     // UI, by checking for its subscribe/unsubscribe checkmark button.
-    var button = exports.check_button_for_sub(sub);
+    const button = exports.check_button_for_sub(sub);
     if (button.length !== 0) {
         return true;
     }
@@ -253,9 +253,9 @@ exports.is_sub_already_present = function (sub) {
 exports.remove_stream = function (stream_id) {
     // It is possible that row is empty when we deactivate a
     // stream, but we let jQuery silently handle that.
-    var row = exports.row_for_stream_id(stream_id);
+    const row = exports.row_for_stream_id(stream_id);
     row.remove();
-    var sub = stream_data.get_sub_by_id(stream_id);
+    const sub = stream_data.get_sub_by_id(stream_id);
     if (stream_edit.is_sub_settings_active(sub)) {
         exports.show_subs_pane.nothing_selected();
     }
@@ -283,10 +283,10 @@ exports.update_settings_for_subscribed = function (sub) {
 };
 
 exports.show_active_stream_in_left_panel = function () {
-    var selected_row = get_hash_safe().split(/\//)[1];
+    const selected_row = get_hash_safe().split(/\//)[1];
 
     if (parseFloat(selected_row)) {
-        var sub_row = exports.row_for_stream_id(selected_row);
+        const sub_row = exports.row_for_stream_id(selected_row);
         sub_row.addClass("active");
     }
 };
@@ -328,10 +328,10 @@ function triage_stream(query, sub) {
         }
     }
 
-    var search_terms = search_util.get_search_terms(query.input);
+    const search_terms = search_util.get_search_terms(query.input);
 
     function match(attr) {
-        var val = sub[attr];
+        const val = sub[attr];
 
         return search_util.vanilla_match({
             val: val,
@@ -354,15 +354,15 @@ function get_stream_id_buckets(stream_ids, query) {
     // When we simplify the settings UI, we can get
     // rid of the "others" bucket.
 
-    var buckets = {
+    const buckets = {
         name: [],
         desc: [],
         other: [],
     };
 
     _.each(stream_ids, function (stream_id) {
-        var sub = stream_data.get_sub_by_id(stream_id);
-        var match_status = triage_stream(query, sub);
+        const sub = stream_data.get_sub_by_id(stream_id);
+        const match_status = triage_stream(query, sub);
 
         if (match_status === 'name_match') {
             buckets.name.push(stream_id);
@@ -380,11 +380,11 @@ function get_stream_id_buckets(stream_ids, query) {
 }
 
 exports.populate_stream_settings_left_panel = function () {
-    var sub_rows = stream_data.get_updated_unsorted_subs();
-    var template_data = {
+    const sub_rows = stream_data.get_updated_unsorted_subs();
+    const template_data = {
         subscriptions: sub_rows,
     };
-    var html = render_subscriptions(template_data);
+    const html = render_subscriptions(template_data);
     ui.get_content_element($('#subscriptions_table .streams-list')).html(html);
 };
 
@@ -393,26 +393,26 @@ exports.populate_stream_settings_left_panel = function () {
 exports.filter_table = function (query) {
     exports.show_active_stream_in_left_panel();
 
-    var widgets = {};
-    var streams_list_scrolltop = ui.get_scroll_element($(".streams-list")).scrollTop();
+    const widgets = {};
+    const streams_list_scrolltop = ui.get_scroll_element($(".streams-list")).scrollTop();
 
-    var stream_ids = [];
+    const stream_ids = [];
     _.each($("#subscriptions_table .stream-row"), function (row) {
-        var stream_id = $(row).attr('data-stream-id');
+        const stream_id = $(row).attr('data-stream-id');
         stream_ids.push(stream_id);
     });
 
-    var buckets = get_stream_id_buckets(stream_ids, query);
+    const buckets = get_stream_id_buckets(stream_ids, query);
 
     // If we just re-built the DOM from scratch we wouldn't need
     // all this hidden/notdisplayed logic.
-    var hidden_ids = {};
+    const hidden_ids = {};
     _.each(buckets.other, function (stream_id) {
         hidden_ids[stream_id] = true;
     });
 
     _.each($("#subscriptions_table .stream-row"), function (row) {
-        var stream_id = $(row).attr('data-stream-id');
+        const stream_id = $(row).attr('data-stream-id');
 
         // Below code goes away if we don't do sort-DOM-in-place.
         if (hidden_ids[stream_id]) {
@@ -428,7 +428,7 @@ exports.filter_table = function (query) {
 
     ui.reset_scrollbar($("#subscription_overlay .streams-list"));
 
-    var all_stream_ids = [].concat(
+    const all_stream_ids = [].concat(
         buckets.name,
         buckets.desc,
         buckets.other
@@ -444,12 +444,12 @@ exports.filter_table = function (query) {
     ui.get_scroll_element($(".streams-list")).scrollTop(streams_list_scrolltop);
 };
 
-var subscribed_only = true;
+let subscribed_only = true;
 
 exports.get_search_params = function () {
-    var search_box = $("#add_new_subscription input[type='text']");
-    var input = search_box.expectOne().val().trim();
-    var params = {
+    const search_box = $("#add_new_subscription input[type='text']");
+    const input = search_box.expectOne().val().trim();
+    const params = {
         input: input,
         subscribed_only: subscribed_only,
     };
@@ -465,11 +465,11 @@ exports.maybe_reset_right_panel = function () {
 };
 
 exports.actually_filter_streams = function () {
-    var search_params = exports.get_search_params();
+    const search_params = exports.get_search_params();
     exports.filter_table(search_params);
 };
 
-var filter_streams = _.throttle(exports.actually_filter_streams, 50);
+const filter_streams = _.throttle(exports.actually_filter_streams, 50);
 
 // Make it explicit that our toggler is not created right away.
 exports.toggler = undefined;
@@ -518,7 +518,7 @@ exports.setup_page = function (callback) {
         });
 
         if (should_list_all_streams()) {
-            var toggler_elem = exports.toggler.get();
+            const toggler_elem = exports.toggler.get();
             $("#subscriptions_table .search-container").prepend(toggler_elem);
         }
         if (page_params.is_guest) {
@@ -533,7 +533,7 @@ exports.setup_page = function (callback) {
 
         $('#subscriptions_table').empty();
 
-        var template_data = {
+        const template_data = {
             can_create_streams: page_params.can_create_streams,
             hide_all_streams: !should_list_all_streams(),
             max_name_length: page_params.stream_name_max_length,
@@ -541,7 +541,7 @@ exports.setup_page = function (callback) {
             is_admin: page_params.is_admin,
         };
 
-        var rendered = render_subscription_table_body(template_data);
+        const rendered = render_subscription_table_body(template_data);
         $('#subscriptions_table').append(rendered);
 
         exports.populate_stream_settings_left_panel();
@@ -567,7 +567,7 @@ exports.setup_page = function (callback) {
 };
 
 exports.switch_to_stream_row = function (stream_id) {
-    var stream_row = exports.row_for_stream_id(stream_id);
+    const stream_row = exports.row_for_stream_id(stream_id);
 
     exports.get_active_data().row.removeClass("active");
     stream_row.addClass("active");
@@ -605,7 +605,7 @@ exports.change_state = function (section) {
 
     // if the section is a valid number.
     if (/\d+/.test(section)) {
-        var stream_id = section;
+        const stream_id = section;
         // Guest users can not access unsubscribed streams
         // So redirect guest users to 'subscribed' tab
         // for any unsubscribed stream settings hash
@@ -640,8 +640,8 @@ exports.close = function () {
 };
 
 exports.switch_rows = function (event) {
-    var active_data = exports.get_active_data();
-    var switch_row;
+    const active_data = exports.get_active_data();
+    let switch_row;
     if (window.location.hash === '#streams/new') {
         // Prevent switching stream rows when creating a new stream
         return false;
@@ -663,9 +663,9 @@ exports.switch_rows = function (event) {
         }
     }
 
-    var row_data = get_row_data(switch_row);
+    const row_data = get_row_data(switch_row);
     if (row_data) {
-        var stream_id = row_data.id;
+        const stream_id = row_data.id;
         exports.switch_to_stream_row(stream_id);
     } else if (event === 'up_arrow' && !row_data) {
         $('#search_stream_name').focus();
@@ -674,8 +674,8 @@ exports.switch_rows = function (event) {
 };
 
 exports.keyboard_sub = function () {
-    var active_data = exports.get_active_data();
-    var row_data = get_row_data(active_data.row);
+    const active_data = exports.get_active_data();
+    const row_data = get_row_data(active_data.row);
     if (row_data) {
         exports.sub_or_unsub(row_data.object);
         if (row_data.object.subscribed && active_data.tab.text() === 'Subscribed') {
@@ -686,7 +686,7 @@ exports.keyboard_sub = function () {
 };
 
 exports.toggle_view = function (event) {
-    var active_data = exports.get_active_data();
+    const active_data = exports.get_active_data();
 
     if (event === 'right_arrow' && active_data.tab.text() === 'Subscribed') {
         exports.toggler.goto('all-streams');
@@ -696,17 +696,17 @@ exports.toggle_view = function (event) {
 };
 
 exports.view_stream = function () {
-    var active_data = exports.get_active_data();
-    var row_data = get_row_data(active_data.row);
+    const active_data = exports.get_active_data();
+    const row_data = get_row_data(active_data.row);
     if (row_data) {
-        var stream_narrow_hash = '#narrow/stream/' + hash_util.encode_stream_name(row_data.object.name);
+        const stream_narrow_hash = '#narrow/stream/' + hash_util.encode_stream_name(row_data.object.name);
         hashchange.go_to_location(stream_narrow_hash);
     }
 };
 
 function ajaxSubscribe(stream, color) {
     // Subscribe yourself to a single stream.
-    var true_stream_name;
+    let true_stream_name;
 
     return channel.post({
         url: "/json/users/me/subscriptions",
@@ -716,7 +716,7 @@ function ajaxSubscribe(stream, color) {
                 $("#create_stream_name").val("");
             }
 
-            var res = JSON.parse(xhr.responseText);
+            const res = JSON.parse(xhr.responseText);
             if (!$.isEmptyObject(res.already_subscribed)) {
                 // Display the canonical stream capitalization.
                 true_stream_name = res.already_subscribed[people.my_current_email()][0];
@@ -752,7 +752,7 @@ exports.do_open_create_stream = function () {
     // Only call this directly for hash changes.
     // Prefer open_create_stream().
 
-    var stream = $.trim($("#search_stream_name").val());
+    const stream = $.trim($("#search_stream_name").val());
 
     if (!should_list_all_streams()) {
         // Realms that don't allow listing streams should simply be subscribed to.
@@ -809,11 +809,11 @@ exports.initialize = function () {
         e.preventDefault();
 
         $('#subscription-status').hide();
-        var stream_name = narrow_state.stream();
+        const stream_name = narrow_state.stream();
         if (stream_name === undefined) {
             return;
         }
-        var sub = stream_data.get_sub(stream_name);
+        const sub = stream_data.get_sub(stream_name);
         exports.sub_or_unsub(sub);
 
         $('.empty_feed_notice').hide();
@@ -831,7 +831,7 @@ exports.initialize = function () {
     });
 
     (function defocus_sub_settings() {
-        var sel = ".search-container, .streams-list, .subscriptions-header";
+        const sel = ".search-container, .streams-list, .subscriptions-header";
 
         $("#subscriptions_table").on("click", sel, function (e) {
             if ($(e.target).is(sel)) {
diff --git a/tools/webpack-helpers.ts b/tools/webpack-helpers.ts
index 38fecbbf91..52f9b015a8 100644
--- a/tools/webpack-helpers.ts
+++ b/tools/webpack-helpers.ts
@@ -27,7 +27,7 @@ interface ExportLoaderOptions {
 }
 function getExposeLoaders(optionsArr: ExportLoaderOptions[]): RuleSetRule[] {
     const exposeLoaders = [];
-    for (var loaderEntry of optionsArr) {
+    for (const loaderEntry of optionsArr) {
         const path = loaderEntry.path;
         let name = "";
         const useArr = [cacheLoader];
@@ -38,7 +38,7 @@ function getExposeLoaders(optionsArr: ExportLoaderOptions[]): RuleSetRule[] {
         } else {
             // If name is an array
             if (Array.isArray(loaderEntry.name)) {
-                for (var exposeName of loaderEntry.name) {
+                for (const exposeName of loaderEntry.name) {
                     useArr.push({loader: 'expose-loader', options: exposeName});
                 }
             // If name is a string
diff --git a/tools/webpack.config.ts b/tools/webpack.config.ts
index 8f8e3f3d7d..0a673e269c 100644
--- a/tools/webpack.config.ts
+++ b/tools/webpack.config.ts
@@ -216,7 +216,7 @@ export default (env?: string): webpack.Configuration[] => {
     // Expose Global variables for third party libraries to webpack modules
     // Use the unminified versions of jquery and underscore so that
     // Good error messages show up in production and development in the source maps
-    var exposeOptions = [
+    const exposeOptions = [
         { path: "blueimp-md5/js/md5.js" },
         { path: "clipboard/dist/clipboard.js", name: "ClipboardJS" },
         { path: "xdate/src/xdate.js", name: "XDate" },