diff --git a/web/src/bundles/app.ts b/web/src/bundles/app.ts
index 1c90d1105c..98d566c093 100644
--- a/web/src/bundles/app.ts
+++ b/web/src/bundles/app.ts
@@ -9,7 +9,7 @@ import "jquery-validation";
 // Import app JS
 import "../setup.ts";
 import "../reload.ts";
-import "../templates.js";
+import "../templates.ts";
 import "../zulip_test.ts";
 
 // Import styles
diff --git a/web/src/templates.js b/web/src/templates.ts
similarity index 65%
rename from web/src/templates.js
rename to web/src/templates.ts
index ef4c6553c6..e866d036d1 100644
--- a/web/src/templates.js
+++ b/web/src/templates.ts
@@ -20,7 +20,7 @@ Handlebars.registerHelper({
     eq(a, b) {
         return a === b;
     },
-    and(...args) {
+    and(...args: unknown[]) {
         args.pop(); // Handlebars options
         if (args.length === 0) {
             return true;
@@ -33,7 +33,7 @@ Handlebars.registerHelper({
         }
         return last;
     },
-    or(...args) {
+    or(...args: unknown[]) {
         args.pop(); // Handlebars options
         if (args.length === 0) {
             return false;
@@ -51,7 +51,9 @@ Handlebars.registerHelper({
     },
 });
 
-Handlebars.registerHelper("t", function (message) {
+type Context = Record<string, unknown>;
+
+Handlebars.registerHelper("t", function (this: Context, message: string) {
     // Marks a string for translation.
     // Example usage 1:
     //     {{t "some English text"}}
@@ -68,10 +70,19 @@ Handlebars.registerHelper("t", function (message) {
         .map((s) => s.trim())
         .join(" ");
     const descriptor = {id: message, defaultMessage: message};
-    return intl.formatMessage(descriptor, this);
+    return intl.formatMessage(
+        descriptor,
+        Object.fromEntries(
+            Object.entries(this).flatMap(([key, value]) =>
+                typeof value === "string" || typeof value === "number" || value instanceof Date
+                    ? [[key, value]]
+                    : [],
+            ),
+        ),
+    );
 });
 
-Handlebars.registerHelper("tr", function (options) {
+Handlebars.registerHelper("tr", function (this: Context, options: Handlebars.HelperOptions) {
     // Marks a block for translation.
     // Example usage 1:
     //     {{#tr}}
@@ -92,19 +103,29 @@ Handlebars.registerHelper("tr", function (options) {
         .map((s) => s.trim())
         .join(" ");
     const descriptor = {id: message, defaultMessage: message};
+    const partials: Partial<Record<string, (context: Context, options: unknown) => string>> =
+        "partials" in options.fn &&
+        typeof options.fn.partials === "object" &&
+        options.fn.partials !== null
+            ? options.fn.partials
+            : {};
     const result = intl.formatMessage(descriptor, {
         ...default_html_elements,
         ...Object.fromEntries(
-            Object.entries(options.fn.partials ?? {}).map(([name, value]) => [
+            Object.entries(partials).map(([name, value]) => [
                 name,
-                (s) => value(this, {data: {"partial-block": () => s.join("")}}),
+                (content_html: string[]) =>
+                    value!(this, {data: {"partial-block": () => content_html.join("")}}),
             ]),
         ),
         ...Object.fromEntries(
-            Object.entries(this).map(([key, value]) => [
-                key,
-                Handlebars.Utils.escapeExpression(value),
-            ]),
+            Object.entries(this).flatMap(([key, value]): [string, string | number | Date][] =>
+                typeof value === "string"
+                    ? [[key, Handlebars.Utils.escapeExpression(value)]]
+                    : typeof value === "number" || value instanceof Date
+                      ? [[key, value]]
+                      : [],
+            ),
         ),
     });
     return new Handlebars.SafeString(result);
@@ -112,13 +133,14 @@ Handlebars.registerHelper("tr", function (options) {
 
 Handlebars.registerHelper(
     "rendered_markdown",
-    (content) => new Handlebars.SafeString(postprocess_content(content)),
+    (content: string) => new Handlebars.SafeString(postprocess_content(content)),
 );
 
-Handlebars.registerHelper("numberFormat", (number) => number.toLocaleString());
+Handlebars.registerHelper("numberFormat", (number: number) => number.toLocaleString());
 
-Handlebars.registerHelper("tooltip_hotkey_hints", (...hotkeys) => {
-    hotkeys.pop(); // Handlebars options
+Handlebars.registerHelper("tooltip_hotkey_hints", (...args) => {
+    args.pop(); // Handlebars options
+    const hotkeys: string[] = args;
     let hotkey_hints = "";
     common.adjust_mac_hotkey_hints(hotkeys);
     for (const hotkey of hotkeys) {
@@ -128,8 +150,9 @@ Handlebars.registerHelper("tooltip_hotkey_hints", (...hotkeys) => {
     return new Handlebars.SafeString(result);
 });
 
-Handlebars.registerHelper("popover_hotkey_hints", (...hotkeys) => {
-    hotkeys.pop(); // Handlebars options
+Handlebars.registerHelper("popover_hotkey_hints", (...args) => {
+    args.pop(); // Handlebars options
+    const hotkeys: string[] = args;
     let hotkey_hints = "";
     common.adjust_mac_hotkey_hints(hotkeys);
     const shift_hotkey_exists = common.adjust_shift_hotkey(hotkeys);
@@ -138,7 +161,7 @@ Handlebars.registerHelper("popover_hotkey_hints", (...hotkeys) => {
     }
     if (shift_hotkey_exists) {
         return new Handlebars.SafeString(
-            `<span class="popover-menu-hotkey-hints popover-contains-shift-hotkey" data-hotkey-hints="${hotkeys}">${hotkey_hints}</span>`,
+            `<span class="popover-menu-hotkey-hints popover-contains-shift-hotkey" data-hotkey-hints="${hotkeys.join(",")}">${hotkey_hints}</span>`,
         );
     }
     return new Handlebars.SafeString(
diff --git a/web/tests/i18n.test.cjs b/web/tests/i18n.test.cjs
index c06fc1c8ad..570c65d59f 100644
--- a/web/tests/i18n.test.cjs
+++ b/web/tests/i18n.test.cjs
@@ -22,12 +22,12 @@ page_params.translation_data = {
 
 // Re-register Zulip extensions so extensions registered previously with
 // mocked i18n.ts do not interfere with following tests.
-require("../src/templates.js");
+require("../src/templates.ts");
 
 // All of our other tests stub out i18n activity;
 // here we do a quick sanity check on the engine itself.
 // `i18n.ts` initializes FormatJS and is imported by
-// `templates.js`.
+// `templates.ts`.
 unmock_module("../src/i18n");
 const {$t, $t_html, get_language_name, get_language_list_columns, initialize} = zrequire("i18n");
 
@@ -102,7 +102,7 @@ run_test("{{#tr}} to tag for translation", ({mock_template}) => {
 
     // We're actually testing `notification_settings.hbs` here which
     // is imported as a partial in the file below. We want to test
-    // the partial handling logic in `templates.js`, that's why we
+    // the partial handling logic in `templates.ts`, that's why we
     // test the file below instead of directly testing
     // `notification_settings.hbs`.
     mock_template("settings/user_notification_settings.hbs", true, (data, html) => {
diff --git a/web/tests/lib/index.cjs b/web/tests/lib/index.cjs
index 21728b569e..e6401a62e1 100644
--- a/web/tests/lib/index.cjs
+++ b/web/tests/lib/index.cjs
@@ -83,7 +83,7 @@ handlebars.hook_require();
 
 const noop = function () {};
 
-require("../../src/templates.js"); // register Zulip extensions
+require("../../src/templates.ts"); // register Zulip extensions
 
 async function run_one_module(file) {
     zjquery.clear_initialize_function();
diff --git a/web/tests/lib/namespace.cjs b/web/tests/lib/namespace.cjs
index 895423e525..7356c2f664 100644
--- a/web/tests/lib/namespace.cjs
+++ b/web/tests/lib/namespace.cjs
@@ -209,7 +209,7 @@ exports.zrequire = function (short_fn) {
         short_fn,
         "templates",
         `
-            There is no need to zrequire templates.js.
+            There is no need to zrequire templates.ts.
 
             The test runner automatically registers the
             Handlebars extensions.
diff --git a/web/webpack.config.ts b/web/webpack.config.ts
index 11b507a317..c10f2afc24 100644
--- a/web/webpack.config.ts
+++ b/web/webpack.config.ts
@@ -167,7 +167,7 @@ const config = (
                         ignoreHelpers: true,
                         // Tell webpack not to explicitly require these.
                         knownHelpers: [
-                            // The ones below are defined in web/src/templates.js
+                            // The ones below are defined in web/src/templates.ts
                             "eq",
                             "and",
                             "or",