diff --git a/tools/test-js-with-node b/tools/test-js-with-node
index 0ba16913b9..b654b087ab 100755
--- a/tools/test-js-with-node
+++ b/tools/test-js-with-node
@@ -95,7 +95,7 @@ EXEMPT_FILES = make_set(
         "web/src/demo_organizations_ui.js",
         "web/src/deprecated_feature_notice.ts",
         "web/src/desktop_integration.js",
-        "web/src/desktop_notifications.js",
+        "web/src/desktop_notifications.ts",
         "web/src/dialog_widget.ts",
         "web/src/drafts.ts",
         "web/src/drafts_overlay_ui.js",
diff --git a/web/src/desktop_notifications.js b/web/src/desktop_notifications.js
deleted file mode 100644
index a8899305b6..0000000000
--- a/web/src/desktop_notifications.js
+++ /dev/null
@@ -1,79 +0,0 @@
-import $ from "jquery";
-
-export const notice_memory = new Map();
-
-export let NotificationAPI;
-
-export function set_notification_api(n) {
-    NotificationAPI = n;
-}
-
-if (window.electron_bridge && window.electron_bridge.new_notification) {
-    class ElectronBridgeNotification extends EventTarget {
-        constructor(title, options) {
-            super();
-            Object.assign(
-                this,
-                window.electron_bridge.new_notification(title, options, (type, eventInit) =>
-                    this.dispatchEvent(new Event(type, eventInit)),
-                ),
-            );
-        }
-
-        static get permission() {
-            return Notification.permission;
-        }
-
-        static async requestPermission(callback) {
-            if (callback) {
-                callback(await Promise.resolve(Notification.permission));
-            }
-            return Notification.permission;
-        }
-    }
-
-    NotificationAPI = ElectronBridgeNotification;
-} else if (window.Notification) {
-    NotificationAPI = window.Notification;
-}
-
-export function get_notifications() {
-    return notice_memory;
-}
-
-export function initialize() {
-    $(window).on("focus", () => {
-        for (const notice_mem_entry of notice_memory.values()) {
-            notice_mem_entry.obj.close();
-        }
-        notice_memory.clear();
-    });
-}
-
-export function permission_state() {
-    if (NotificationAPI === undefined) {
-        // act like notifications are blocked if they do not have access to
-        // the notification API.
-        return "denied";
-    }
-    return NotificationAPI.permission;
-}
-
-export function close_notification(message) {
-    for (const [key, notice_mem_entry] of notice_memory) {
-        if (notice_mem_entry.message_id === message.id) {
-            notice_mem_entry.obj.close();
-            notice_memory.delete(key);
-        }
-    }
-}
-
-export function granted_desktop_notifications_permission() {
-    return NotificationAPI && NotificationAPI.permission === "granted";
-}
-
-export function request_desktop_notifications_permission() {
-    if (NotificationAPI) {
-        NotificationAPI.requestPermission();
-    }
-}
diff --git a/web/src/desktop_notifications.ts b/web/src/desktop_notifications.ts
new file mode 100644
index 0000000000..94a8a4680e
--- /dev/null
+++ b/web/src/desktop_notifications.ts
@@ -0,0 +1,111 @@
+import $ from "jquery";
+import assert from "minimalistic-assert";
+
+import type {Message} from "./message_store";
+
+type NoticeMemory = Map<
+    string,
+    {
+        obj: Notification | ElectronBridgeNotification;
+        msg_count: number;
+        message_id: number;
+    }
+>;
+
+export const notice_memory: NoticeMemory = new Map();
+
+export let NotificationAPI: typeof ElectronBridgeNotification | typeof Notification | undefined;
+
+// Used for testing
+export function set_notification_api(n: typeof NotificationAPI): void {
+    NotificationAPI = n;
+}
+
+class ElectronBridgeNotification extends EventTarget {
+    title: string;
+    dir: NotificationDirection;
+    lang: string;
+    body: string;
+    tag: string;
+    icon: string;
+    data: unknown;
+    close: () => void;
+
+    constructor(title: string, options: NotificationOptions) {
+        super();
+        assert(window.electron_bridge?.new_notification !== undefined);
+        const notification_data = window.electron_bridge.new_notification(
+            title,
+            options,
+            (type, eventInit) => this.dispatchEvent(new Event(type, eventInit)),
+        );
+        this.title = notification_data.title;
+        this.dir = notification_data.dir;
+        this.lang = notification_data.lang;
+        this.body = notification_data.body;
+        this.tag = notification_data.tag;
+        this.icon = notification_data.icon;
+        this.data = notification_data.data;
+        this.close = notification_data.close;
+    }
+
+    static get permission(): NotificationPermission {
+        return Notification.permission;
+    }
+
+    static async requestPermission(
+        callback?: (permission: NotificationPermission) => void,
+    ): Promise<NotificationPermission> {
+        if (callback) {
+            callback(await Promise.resolve(Notification.permission));
+        }
+        return Notification.permission;
+    }
+}
+
+if (window.electron_bridge?.new_notification) {
+    NotificationAPI = ElectronBridgeNotification;
+} else if (window.Notification) {
+    NotificationAPI = window.Notification;
+}
+
+export function get_notifications(): NoticeMemory {
+    return notice_memory;
+}
+
+export function initialize(): void {
+    $(window).on("focus", () => {
+        for (const notice_mem_entry of notice_memory.values()) {
+            notice_mem_entry.obj.close();
+        }
+        notice_memory.clear();
+    });
+}
+
+export function permission_state(): string {
+    if (NotificationAPI === undefined) {
+        // act like notifications are blocked if they do not have access to
+        // the notification API.
+        return "denied";
+    }
+    return NotificationAPI.permission;
+}
+
+export function close_notification(message: Message): void {
+    for (const [key, notice_mem_entry] of notice_memory) {
+        if (notice_mem_entry.message_id === message.id) {
+            notice_mem_entry.obj.close();
+            notice_memory.delete(key);
+        }
+    }
+}
+
+export function granted_desktop_notifications_permission(): boolean {
+    return NotificationAPI?.permission === "granted";
+}
+
+export function request_desktop_notifications_permission(): void {
+    if (NotificationAPI) {
+        void NotificationAPI.requestPermission();
+    }
+}