check for new user firebase code example

Example 1: restrict the user from going to signup or login page if the user is already logged in firebase auth

var user = firebase.auth().currentUser;

if (user) {
  // User is signed in.
} else {
  // No user is signed in.
}

Example 2: firebase auth get current user

var user = firebase.auth().currentUser;var name, email, photoUrl, uid, emailVerified;if (user != null) {  name = user.displayName;  email = user.email;  photoUrl = user.photoURL;  emailVerified = user.emailVerified;  uid = user.uid;  // The user's ID, unique to the Firebase project. Do NOT use                   // this value to authenticate with your backend server, if                   // you have one. Use User.getToken() instead.}

Example 3: firebase auth update

In the newest version of firebase_auth:

FirebaseUser has been changed to User

AuthResult has been changed to UserCredential

GoogleAuthProvider.getCredential() has been changed to GoogleAuthProvider.credential()

onAuthStateChanged which notifies about changes to the user's sign-in state was replaced with authStateChanges()

currentUser() which is a method to retrieve the currently logged in user, was replaced with the property currentUser and it no longer returns a Future<FirebaseUser>

Example 4: firebase auth update current user

var user = firebase.auth().currentUser;user.updateProfile({  displayName: "Jane Q. User",  photoURL: "https://example.com/jane-q-user/profile.jpg"}).then(function() {  // Update successful.}).catch(function(error) {  // An error happened.});