Firebase Cookbook

How to do it...

1. In order to do this, we will use the Firebase auth APIs like we did previously, as shown in the following code snippet: 

      //Get a button reference.      let anonLogin =           document.getElementById('anonymousLogin');      anonLogin.addEventListener('click', () => {         firebase.auth().signInAnonymously()            .catch(err => {               //Catch and showcase the error.            });      }, false);

2. Now, we need another way to check whether the user is logged in or not. To do that we'll need to check the authentication state of the user, using the onAuthStateChanged event as shown in the following code: 

      firebase.auth().onAuthStateChanged((user) => {        if (user) {     // Since we have the user object, we have a stable                               connection, and we're // authenticated.          var uid = user