Auth with Firebase 3.x and Cordova/Ionic using ngCordova oauth.

auth.js

this.$cordovaOauth.facebook("your_client_id", ["email"])
  .then(function (result) {
    var credentials = firebase.auth.FacebookAuthProvider.credential(result.access_token);
    return firebase.auth().signInWithCredential(credentials);
  })
  .then(function (firebaseUser) {
    console.log("Signed in as:", firebaseUser.uid);
  })
  .catch(function (error) {
    console.error("Authentication failed:", error);
  });