index.js

// These samples are intended for Web so this import would normally be
// done in HTML however using modules here is more convenient for
// ensuring sample correctness offline.
import firebase from "firebase/app";
import "firebase/auth";

// ==========================================================================================
// Docs: Snippets in this file are "general purpose" and are used on more than one docs page
// ==========================================================================================

function makeGoogleCredential(googleUser) {
  // [START auth_make_google_credential]
  var credential = firebase.auth.GoogleAuthProvider.credential(
    googleUser.getAuthResponse().id_token);
  // [END auth_make_google_credential]
}

function makeFacebookCredential(response) {
  // [START auth_make_facebook_credential]
  var credential = firebase.auth.FacebookAuthProvider.credential(
    response.authResponse.accessToken);
  // [END auth_make_facebook_credential]
}

function makeEmailCredential(email, password) {
  // [START auth_make_email_credential]
  var credential = firebase.auth.EmailAuthProvider.credential(email, password);
  // [END auth_make_email_credential]
}

function signOut() {
  // [START auth_sign_out]
  firebase.auth().signOut().then(() => {
    // Sign-out successful.
  }).catch((error) => {
    // An error happened.
  });
  // [END auth_sign_out]
}

function authStateListener() {
  // [START auth_state_listener]
  firebase.auth().onAuthStateChanged((user) => {
    if (user) {
      // User is signed in, see docs for a list of available properties
      // https://firebase.google.com/docs/reference/js/firebase.User
      var uid = user.uid;
      // ...
    } else {
      // User is signed out
      // ...
    }
  });
  // [END auth_state_listener]
}

function currentUser() {
  // [START auth_current_user]
  const user = firebase.auth().currentUser;

  if (user) {
    // User is signed in, see docs for a list of available properties
    // https://firebase.google.com/docs/reference/js/firebase.User
    // ...
  } else {
    // No user is signed in.
  }
  // [END auth_current_user]
}

function setLanguageCode() {
  // [START auth_set_language_code]
  firebase.auth().languageCode = 'it';
  // To apply the default browser preference instead of explicitly setting it.
  // firebase.auth().useDeviceLanguage();
  // [END auth_set_language_code]
}

function authWithCredential(credential) {
  // [START auth_signin_credential]
  // Sign in with the credential from the user.
  firebase.auth()
    .signInWithCredential(credential)
    .then((result) => {
      // Signed in 
      // ...
    })
    .catch((error) => {
      // Handle Errors here.
      const errorCode = error.code;
      const errorMessage = error.message;
      // The email of the user's account used.
      const email = error.email;
      // ...
    });
  // [END auth_signin_credential]
}

function signInRedirect(provider) {
  // [START auth_signin_redirect]
  firebase.auth().signInWithRedirect(provider);
  // [END auth_signin_redirect]
}

function initializeWithCustomDomain() {
  // [START auth_init_custom_domain]
  firebase.initializeApp({
    apiKey: '...',
    // By default, authDomain is '[YOUR_APP].firebaseapp.com'.
    // You may replace it with a custom domain.
    authDomain: '[YOUR_CUSTOM_DOMAIN]'
  });
  // [END auth_init_custom_domain]
}