refactor: Move popular_emojis to typeahead library.

I removed a slightly confusing code comment, which I
will address in a follow up commit.  Basically,
"slight smile" still doesn't win over "small airplane"
when you search for "sm", which kind of defeats the
purpose of having popular_emojis for the typeahead
use case.  This is a problem with sort_emojis, though,
so when the comment was next to the list of popular
emojis, it wasn't really actionable.

static/js/emoji.js

@@ -7,19 +7,6 @@ exports.all_realm_emojis = {};
 exports.active_realm_emojis = {};
 exports.default_emoji_aliases = {};
 
-// Unfortunately, this list does not currently match on
-// alias names like party_popper, simple_smile, and
-// hammer_and_wrench. But thumbs_up sorts to the top
-// for some other reason.
-exports.frequently_used_emojis_list = [
-    '1f44d',    // +1
-    '1f389',    // tada
-    '1f642',    // slight_smile
-    '2764',     // heart
-    '1f6e0',    // working_on_it
-    '1f419',    // octopus
-];
-
 const zulip_emoji = {
     id: 'zulip',
     emoji_name: 'zulip',

static/js/emoji_picker.js

@@ -1,3 +1,5 @@
+const typeahead = require("../shared/js/typeahead");
+
 const render_emoji_popover = require('../templates/emoji_popover.hbs');
 const render_emoji_popover_content = require('../templates/emoji_popover_content.hbs');
 const render_emoji_popover_search_results = require('../templates/emoji_popover_search_results.hbs');
@@ -119,7 +121,7 @@ exports.generate_emoji_picker_data = function (realm_emojis) {
     });
 
     exports.complete_emoji_catalog.Popular = [];
-    _.each(emoji.frequently_used_emojis_list, function (codepoint) {
+    _.each(typeahead.popular_emojis, function (codepoint) {
         if (emoji_codes.codepoint_to_name.hasOwnProperty(codepoint)) {
             const emoji_name = emoji_codes.codepoint_to_name[codepoint];
             if (emoji.emojis_by_name.hasOwnProperty(emoji_name)) {

static/js/typeahead_helper.js

@@ -167,7 +167,7 @@ exports.sort_emojis = function (objs, query) {
     const other_emoji_matches = [];
 
     for (const obj of triage_results.matches) {
-        if (emoji.frequently_used_emojis_list.indexOf(obj.emoji_code) !== -1) {
+        if (typeahead.popular_emojis.indexOf(obj.emoji_code) !== -1) {
             popular_emoji_matches.push(obj);
         } else {
             other_emoji_matches.push(obj);

static/shared/js/typeahead.js

@@ -1,3 +1,33 @@
+/*
+    We hand selected the following emojis a few years
+    ago to be given extra precedence in our typeahead
+    algorithms and emoji picker UIs.  We call them "popular"
+    emojis for historical reasons, although we've never
+    technically measured their popularity (and any
+    results now would be biased in favor of the ones
+    below, since they've easier to submit).  Nonetheless, it
+    is often convenient to quickly find these.  We can
+    adjust this list over time; we just need to make
+    sure it works well with the emoji picker's layout
+    if you increase the number of them.
+
+    For typeahead we'll favor any of these as long as
+    the emoji code matches.  For example, we'll show the
+    emoji with code 1f44d at the top of your suggestions
+    whether you type "+" as a prefix for "+1"
+    or "th" as a prefix for "thumbs up".  The caveat is
+    that other factors still may matter more, such as
+    prefix matches trumping "popularity".
+*/
+exports.popular_emojis = [
+    '1f44d', // +1
+    '1f389', // tada
+    '1f642', // slight_smile
+    '2764', // heart
+    '1f6e0', // working_on_it
+    '1f419', // octopus
+];
+
 const unicode_marks = /\p{M}/gu;
 
 exports.remove_diacritics = function (s) {