How do I call fetchSignInMethodsForEmail() from Firebase Auth

Question

I have a PSK (Polymer Starter Kit) PWA build with polymerfire, I want to call fetchSignInMethodsForEmail() from Firebase Auth. I have tried the following but with error.

firebase.auth().fetchSignInMethodsForEmail(email).then((methods) => {
  // Do something
});

with the error Uncaught TypeError: firebase.auth(...).fetchSignInMethodsForEmail is not a function.

I have tried the following as well with no luck, i.e.

firebase.auth.fetchSignInMethodsForEmail(email);
firebase.$.auth.fetchSignInMethodsForEmail(email); // Assume firebase-auth with id of 'auth'

Answer 1

fetchProvidersForEmail() was introduced in Firebase JavaScript SDK v4.12 so you need to have at least v4.12 and above.

Being said that it is deprecated in v5.0 in favor of fetchSignInMethodsForEmail().

Answer 2

First, you have to declare Auth object.

 FirebaseAuth f = FirebaseAuth.getInstance();

Then call the fetchSignInMethodsForEmail(), method.

as follows:

 // [START auth_differentiate_link]

auth.fetchSignInMethodsForEmail(email)
.addOnCompleteListener(new OnCompleteListener<SignInMethodQueryResult>() {
    @Override
            public void onComplete(@NonNull Task<SignInMethodQueryResult> task) {
               if (task.isSuccessful()) {
                  SignInMethodQueryResult result = task.getResult();
                  List<String> signInMethods = result.getSignInMethods();
           if(signInMethods.contains(EmailAuthProvider.EMAIL_PASSWORD_SIGN_IN_METHOD)) 
                {
                   // User can sign in with email/password
                } else if (signInMethods.contains(EmailAuthProvider.EMAIL_LINK_SIGN_IN_METHOD)) {
                  // User can sign in with email/link
                }
               } else {
                  Log.e(TAG, "Error getting sign in methods for user", task.getException());
               }
           }
        });
  // [END auth_differentiate_link]
}

Answer 3

For people using the new modular version it's done like this:

import {  fetchSignInMethodsForEmail } from 'firebase/auth';

    fetchSignInMethodsForEmail(auth, email).then((result) => {
      console.log(result);
    });