diff --git a/tools/test-js-with-node b/tools/test-js-with-node
index 68a0351156..206630c176 100755
--- a/tools/test-js-with-node
+++ b/tools/test-js-with-node
@@ -255,7 +255,7 @@ EXEMPT_FILES = make_set(
         "web/src/tippyjs.ts",
         "web/src/todo_widget.ts",
         "web/src/topic_list.ts",
-        "web/src/topic_popover.js",
+        "web/src/topic_popover.ts",
         "web/src/typing.ts",
         "web/src/typing_events.ts",
         "web/src/ui_init.js",
diff --git a/web/src/message_edit.ts b/web/src/message_edit.ts
index 26785ba26c..6f90358816 100644
--- a/web/src/message_edit.ts
+++ b/web/src/message_edit.ts
@@ -785,7 +785,7 @@ export function toggle_resolve_topic(
     message_id: number,
     old_topic_name: string,
     report_errors_in_global_banner: boolean,
-    $row: JQuery,
+    $row?: JQuery,
 ): void {
     let new_topic_name;
     const topic_is_resolved = resolved_topic.is_resolved(old_topic_name);
@@ -826,7 +826,7 @@ function do_toggle_resolve_topic(
     new_topic_name: string,
     topic_is_resolved: boolean,
     report_errors_in_global_banner: boolean,
-    $row: JQuery,
+    $row?: JQuery,
 ): void {
     if ($row) {
         show_toggle_resolve_topic_spinner($row);
diff --git a/web/src/stream_popover.ts b/web/src/stream_popover.ts
index aeeb906fef..76bf4bea06 100644
--- a/web/src/stream_popover.ts
+++ b/web/src/stream_popover.ts
@@ -342,7 +342,7 @@ export async function build_move_topic_to_stream_popover(
     current_stream_id: number,
     topic_name: string,
     only_topic_edit: boolean,
-    message: Message | undefined,
+    message?: Message,
 ): Promise<void> {
     const current_stream_name = sub_store.get(current_stream_id)!.name;
     const args: {
diff --git a/web/src/topic_popover.js b/web/src/topic_popover.ts
similarity index 74%
rename from web/src/topic_popover.js
rename to web/src/topic_popover.ts
index b47fa73442..0e2d1062b3 100644
--- a/web/src/topic_popover.js
+++ b/web/src/topic_popover.ts
@@ -1,5 +1,7 @@
 import ClipboardJS from "clipboard";
 import $ from "jquery";
+import assert from "minimalistic-assert";
+import type * as tippy from "tippy.js";
 
 import render_delete_topic_modal from "../templates/confirm_dialog/confirm_delete_topic.hbs";
 import render_left_sidebar_topic_actions_popover from "../templates/popovers/left_sidebar/left_sidebar_topic_actions_popover.hbs";
@@ -17,7 +19,32 @@ import * as unread_ops from "./unread_ops.ts";
 import * as user_topics from "./user_topics.ts";
 import * as util from "./util.ts";
 
-export function initialize() {
+function get_conversation(instance: tippy.Instance): {
+    stream_id: number;
+    topic_name: string;
+    url: string;
+} {
+    let stream_id;
+    let topic_name;
+    let url;
+
+    if (instance.reference.classList.contains("inbox-topic-menu")) {
+        const $elt = $(instance.reference);
+        stream_id = Number.parseInt($elt.attr("data-stream-id")!, 10);
+        topic_name = $elt.attr("data-topic-name")!;
+        url = new URL($elt.attr("data-topic-url")!, realm.realm_url).href;
+    } else {
+        const $elt = $(instance.reference).closest(".topic-sidebar-menu-icon").expectOne();
+        const $stream_li = $elt.closest(".narrow-filter").expectOne();
+        topic_name = $elt.closest("li").expectOne().attr("data-topic-name")!;
+        url = util.the($elt.closest("li").find<HTMLAnchorElement>("a.sidebar-topic-name")).href;
+        stream_id = stream_popover.elem_to_stream_id($stream_li);
+    }
+
+    return {stream_id, topic_name, url};
+}
+
+export function initialize(): void {
     popover_menus.register_popover_menu(
         "#stream_filters .topic-sidebar-menu-icon, .inbox-row .inbox-topic-menu",
         {
@@ -26,37 +53,17 @@ export function initialize() {
                 popover_menus.popover_instances.topics_menu = instance;
                 ui_util.show_left_sidebar_menu_icon(instance.reference);
                 popover_menus.on_show_prep(instance);
-                let stream_id;
-                let topic_name;
-                let url;
 
-                if (instance.reference.classList.contains("inbox-topic-menu")) {
-                    const $elt = $(instance.reference);
-                    stream_id = Number.parseInt($elt.attr("data-stream-id"), 10);
-                    topic_name = $elt.attr("data-topic-name");
-                    url = new URL($elt.attr("data-topic-url"), realm.realm_url);
-                } else {
-                    const $elt = $(instance.reference)
-                        .closest(".topic-sidebar-menu-icon")
-                        .expectOne();
-                    const $stream_li = $elt.closest(".narrow-filter").expectOne();
-                    topic_name = $elt.closest("li").expectOne().attr("data-topic-name");
-                    url = $elt.closest("li").find(".sidebar-topic-name").expectOne().prop("href");
-                    stream_id = stream_popover.elem_to_stream_id($stream_li);
-                }
-
-                instance.context = popover_menus_data.get_topic_popover_content_context({
-                    stream_id,
-                    topic_name,
-                    url,
-                });
+                const context = popover_menus_data.get_topic_popover_content_context(
+                    get_conversation(instance),
+                );
                 instance.setContent(
-                    ui_util.parse_html(render_left_sidebar_topic_actions_popover(instance.context)),
+                    ui_util.parse_html(render_left_sidebar_topic_actions_popover(context)),
                 );
             },
             onMount(instance) {
                 const $popper = $(instance.popper);
-                const {stream_id, topic_name} = instance.context;
+                const {stream_id, topic_name} = get_conversation(instance);
 
                 if (!stream_id) {
                     popover_menus.hide_current_popover_if_visible(instance);
@@ -66,11 +73,11 @@ export function initialize() {
                 $popper.on("change", "input[name='sidebar-topic-visibility-select']", (e) => {
                     const start_time = Date.now();
                     const visibility_policy = Number.parseInt(
-                        $(e.currentTarget).attr("data-visibility-policy"),
+                        $(e.currentTarget).attr("data-visibility-policy")!,
                         10,
                     );
 
-                    const success_cb = () => {
+                    const success_cb = (): void => {
                         setTimeout(
                             () => {
                                 popover_menus.hide_current_popover_if_visible(instance);
@@ -79,7 +86,7 @@ export function initialize() {
                         );
                     };
 
-                    const error_cb = () => {
+                    const error_cb = (): void => {
                         const prev_visibility_policy = user_topics.get_topic_visibility_policy(
                             stream_id,
                             topic_name,
@@ -108,10 +115,7 @@ export function initialize() {
                 });
 
                 $popper.one("click", ".sidebar-popover-unstar-all-in-topic", () => {
-                    starred_messages_ui.confirm_unstar_all_messages_in_topic(
-                        Number.parseInt(stream_id, 10),
-                        topic_name,
-                    );
+                    starred_messages_ui.confirm_unstar_all_messages_in_topic(stream_id, topic_name);
                     popover_menus.hide_current_popover_if_visible(instance);
                 });
 
@@ -142,6 +146,7 @@ export function initialize() {
 
                 $popper.one("click", ".sidebar-popover-toggle-resolved", () => {
                     message_edit.with_first_message_id(stream_id, topic_name, (message_id) => {
+                        assert(message_id !== undefined);
                         message_edit.toggle_resolve_topic(message_id, topic_name, true);
                     });
 
@@ -149,16 +154,24 @@ export function initialize() {
                 });
 
                 $popper.one("click", ".sidebar-popover-move-topic-messages", () => {
-                    stream_popover.build_move_topic_to_stream_popover(stream_id, topic_name, false);
+                    void stream_popover.build_move_topic_to_stream_popover(
+                        stream_id,
+                        topic_name,
+                        false,
+                    );
                     popover_menus.hide_current_popover_if_visible(instance);
                 });
 
                 $popper.one("click", ".sidebar-popover-rename-topic-messages", () => {
-                    stream_popover.build_move_topic_to_stream_popover(stream_id, topic_name, true);
+                    void stream_popover.build_move_topic_to_stream_popover(
+                        stream_id,
+                        topic_name,
+                        true,
+                    );
                     popover_menus.hide_current_popover_if_visible(instance);
                 });
 
-                new ClipboardJS($popper.find(".sidebar-popover-copy-link-to-topic")[0]).on(
+                new ClipboardJS(util.the($popper.find(".sidebar-popover-copy-link-to-topic"))).on(
                     "success",
                     () => {
                         popover_menus.hide_current_popover_if_visible(instance);
@@ -167,7 +180,7 @@ export function initialize() {
             },
             onHidden(instance) {
                 instance.destroy();
-                popover_menus.popover_instances.topics_menu = undefined;
+                popover_menus.popover_instances.topics_menu = null;
                 ui_util.hide_left_sidebar_menu_icon();
             },
         },
diff --git a/web/src/ui_init.js b/web/src/ui_init.js
index 0c0706731b..224c3dc3ed 100644
--- a/web/src/ui_init.js
+++ b/web/src/ui_init.js
@@ -133,7 +133,7 @@ import * as thumbnail from "./thumbnail.ts";
 import * as timerender from "./timerender.ts";
 import * as tippyjs from "./tippyjs.ts";
 import * as topic_list from "./topic_list.ts";
-import * as topic_popover from "./topic_popover.js";
+import * as topic_popover from "./topic_popover.ts";
 import * as transmit from "./transmit.js";
 import * as typeahead_helper from "./typeahead_helper.ts";
 import * as typing from "./typing.ts";
diff --git a/web/src/ui_util.ts b/web/src/ui_util.ts
index 329fec5f39..af01023c76 100644
--- a/web/src/ui_util.ts
+++ b/web/src/ui_util.ts
@@ -202,7 +202,7 @@ export function listener_for_preferred_color_scheme_change(callback: () => void)
 }
 
 // Keep the menu icon over which the popover is based off visible.
-export function show_left_sidebar_menu_icon(element: HTMLElement): void {
+export function show_left_sidebar_menu_icon(element: Element): void {
     $(element).closest(".sidebar-menu-icon").addClass("left_sidebar_menu_icon_visible");
 }