3.2. Firebase Auth: Google Sign In.md

Auth with Using Google Sign-In

If you are building a web app, the easiest way to authenticate your users with Firebase using their Google Accounts is to handle the sign-in flow with the Firebase JavaScript SDK. (If you want to authenticate a user in Node.js or other non-browser environment, you must handle the sign-in flow manually.)

To handle the sign-in flow with the Firebase JavaScript SDK, follow these steps:

1. Create an instance of the Google provider object:

     var provider = new firebase.auth.GoogleAuthProvider();

2. Authenticate with Firebase using the Google provider object. You can prompt your users to sign in with their Google Accounts either by opening a pop-up window or by redirecting to the sign-in page. The redirect method is preferred on mobile devices.

   To sign in with a pop-up window, call signInWithPopup:

   firebase.auth().signInWithPopup(provider).then(function(result) {
      // This gives you a Google Access Token. You can use it to access the Google API.
      var token = result.credential.accessToken;
      // The signed-in user info.
      var user = result.user;
      // ...
    }).catch(function(error) {
      // Handle Errors here.
      var errorCode = error.code;
      var errorMessage = error.message;
      // The email of the user's account used.
      var email = error.email;
      // The firebase.auth.AuthCredential type that was used.
      var credential = error.credential;
      // ...
    });

   To sign in by redirecting to the sign-in page, call signInWithRedirect:

    firebase.auth().getRedirectResult().then(function(result) {
      if (result.credential) {
        // This gives you a Google Access Token. You can use it to access the Google API.
        var token = result.credential.accessToken;
        // ...
      }
      // The signed-in user info.
      var user = result.user;
    }).catch(function(error) {
      // Handle Errors here.
      var errorCode = error.code;
      var errorMessage = error.message;
      // The email of the user's account used.
      var email = error.email;
      // The firebase.auth.AuthCredential type that was used.
      var credential = error.credential;
      // ...
    });

   2.2.2) Sign Out User

   To sign out a user, call signOut:

    firebase.auth().signOut().then(function() {
      // Sign-out successful.
    }).catch(function(error) {
      // An error happened.
    });