Firebase getIdToken not working

Question

I'm makeing tests with Firebase Authentication from javascript client and I'm trying to retrieve the idToken with retrieve id tokens on clients documentation

I think I'm forgetting something basic.

A user is logged in with Google

The code is just i've seen in other posts and in the documentation. And the result is in the comments.

firebase.auth().onAuthStateChanged(function(user) {
  if (user) {
     console.log(user); // this is shown. Firebase user and provider data
     console.log(user.uid); // Shown
        firebase.auth().user.getIdToken().then(function(idToken) {
           console.log(idToken+'--'); // Nothing happens. No errors and the function not continues
        });
     console.log(user.uid); // Nothing happens
  }
})

Thanks

EDIT:

if I add anything wrong nothing happens too. for example if I add an alert it shows the alert but if I have a mistake, for example alter() not shows any error. Added catch and nothing too

firebase.auth().onAuthStateChanged(function(user) {
  if (user) {
     alter() // Nothing happens and the function stop         
     console.log(user); // this is shown. Firebase user and provider data
     console.log(user.uid); // Shown
        firebase.auth().user.getIdToken().then(function(idToken) {
           console.log(idToken+'--'); // Nothing happens. No errors and the function not continues
        }).catch(function(error) {
            console.log(error+'--'); // Nothing
        });
     console.log(user.uid); // Nothing happens
  }
})

Answer 1

firebase.auth().user doesn't have the user in that moment yet. You have to use the user from firebase.auth().onAuthStateChanged directly like this:

firebase.auth().onAuthStateChanged(function(user) {
    if (user) {
        console.log(user); // It shows the Firebase user
        console.log(firebase.auth().user); // It is still undefined
        user.getIdToken().then(function(idToken) {  // <------ Check this line
           console.log(idToken); // It shows the Firebase token now
        });
    }
});

You can only use firebase.auth().user after firebase.auth().onAuthStateChanged is completed and outside of its scope, otherwise it will be undefined.