ReferenceError: window is not defined, Firebase analytics

I get the error ReferenceError: window is not defined when trying to initialize Firebase analytics in my Next.js project.

Here’s the relevant code snippet:

const app = initializeApp(firebaseConfig);
const auth = getAuth(app);
let analytics;
if (window !== undefined) {
   analytics = getAnalytics(app);
}

onAuthStateChanged(auth, (user) => {
  if (user) {
    // User signed in
    const uid = user.uid;
    console.log(uid);
  } else {
    // User signed out.
  }
});

export { app, auth, analytics };

The issue was resolved in another post; but the proposed solution doesn’t seem to be working for me.

>Solution :

If window doesn’t exist, you can’t check its type.

Consider:

if (typeof window !== 'undefined') {