diff --git a/tools/test-js-with-node b/tools/test-js-with-node
index aed230bcd6..d80949d188 100755
--- a/tools/test-js-with-node
+++ b/tools/test-js-with-node
@@ -221,7 +221,7 @@ EXEMPT_FILES = make_set(
         "web/src/settings_user_topics.js",
         "web/src/settings_users.js",
         "web/src/setup.ts",
-        "web/src/sidebar_ui.js",
+        "web/src/sidebar_ui.ts",
         "web/src/spectators.ts",
         "web/src/spoilers.ts",
         "web/src/starred_messages_ui.js",
diff --git a/web/src/sidebar_ui.js b/web/src/sidebar_ui.ts
similarity index 91%
rename from web/src/sidebar_ui.js
rename to web/src/sidebar_ui.ts
index 44c594da46..b71e47a954 100644
--- a/web/src/sidebar_ui.js
+++ b/web/src/sidebar_ui.ts
@@ -15,33 +15,33 @@ import {user_settings} from "./user_settings";
 export let left_sidebar_expanded_as_overlay = false;
 export let right_sidebar_expanded_as_overlay = false;
 
-export function hide_userlist_sidebar() {
+export function hide_userlist_sidebar(): void {
     $(".app-main .column-right").removeClass("expanded");
     right_sidebar_expanded_as_overlay = false;
 }
 
-export function show_userlist_sidebar() {
+export function show_userlist_sidebar(): void {
     $(".app-main .column-right").addClass("expanded");
     resize.resize_page_components();
     right_sidebar_expanded_as_overlay = true;
 }
 
-export function show_streamlist_sidebar() {
+export function show_streamlist_sidebar(): void {
     $(".app-main .column-left").addClass("expanded");
     resize.resize_stream_filters_container();
     left_sidebar_expanded_as_overlay = true;
 }
 
-export function hide_streamlist_sidebar() {
+export function hide_streamlist_sidebar(): void {
     $(".app-main .column-left").removeClass("expanded");
     left_sidebar_expanded_as_overlay = false;
 }
 
-export function any_sidebar_expanded_as_overlay() {
+export function any_sidebar_expanded_as_overlay(): boolean {
     return left_sidebar_expanded_as_overlay || right_sidebar_expanded_as_overlay;
 }
 
-export function update_invite_user_option() {
+export function update_invite_user_option(): void {
     if (
         !settings_data.user_can_invite_users_by_email() &&
         !settings_data.user_can_create_multiuse_invite()
@@ -52,12 +52,12 @@ export function update_invite_user_option() {
     }
 }
 
-export function hide_all() {
+export function hide_all(): void {
     hide_streamlist_sidebar();
     hide_userlist_sidebar();
 }
 
-export function initialize() {
+export function initialize(): void {
     $("body").on("click", ".login_button", (e) => {
         e.preventDefault();
         e.stopPropagation();
@@ -94,6 +94,10 @@ export function initialize() {
                 return;
             }
 
+            if (!(e.target instanceof Element)) {
+                return;
+            }
+
             const $elt = $(e.target);
             // Since sidebar toggle buttons have their own click handlers, don't handle them here.
             if (
@@ -135,7 +139,7 @@ export function initialize() {
     );
 }
 
-export function initialize_left_sidebar() {
+export function initialize_left_sidebar(): void {
     const rendered_sidebar = render_left_sidebar({
         is_guest: current_user.is_guest,
         development_environment: page_params.development_environment,
@@ -151,7 +155,7 @@ export function initialize_left_sidebar() {
     $("#left-sidebar-container").html(rendered_sidebar);
 }
 
-export function initialize_right_sidebar() {
+export function initialize_right_sidebar(): void {
     const rendered_sidebar = render_right_sidebar({
         realm_rendered_description: page_params.realm_rendered_description,
     });