how to retrieve and handle Redirect errors using firebase Auth?

Question

I'm developing mobile first app, using Firebase Auth. Firebase recommends redirect instead of popup. However, I can't seem to find any example of retrieving errors on using Oauth providers (facebook ,Google). Firebase has an example of handling error in SignwithPopup , but fore redirect it only states:

This error is handled in a similar way in the redirect mode, with the difference that the pending credential has to be cached between page redirects (for example, using session storage).

Answer 1

We show where to do error handling for redirect operation in the previous section of the same doc: Just search for "firebase.auth().getRedirectResult()" in this page specifically in the catch here:

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;
  // ...
});

By the way, adding multiple auth providers and handling linking accounts perfectly is actually quite tricky because there are many sub-flows to take into account (e.g. what if the user wants to link but then signs-in an account where the emails do not match...). I recommend you use Firebase UI which provides a configurable UI component that will handle all these tricky flows for you.