Firebase saying user is null after successful login

Question

I'm trying to upload my user's files to a bucket connected to their uid. So, in order to do it I try to grab their uid from the following code in my upload.js file:

const uploader = document.getElementById("uploader");
const fileButton = document.getElementById("fileButton");


fileButton.addEventListener('change', function(e)
{
  // Get file
  var file = e.target.files[0];

  firebase.auth().onAuthStateChanged(function(user) {
    if (user) {
      // User is signed in.
      console.log("state = definitely signed in");
      firebase.storage().ref('users').child(user.uid + "designs").put(file);
    } else {
      // No user is signed in.
      console.log("state = definitely signed out");
    }
  });
});

Even after the user is logged in and the it directs them to the new page I always get informed that they aren't signed in. Should I use information from the session cookie instead? Any help would be appreciated!

Answer 1

After a few days I realised that I wasn't calling the id token correlated with the user that is logged in. This solved it:

  firebase.auth().onAuthStateChanged(function(user)
  {
    if (user)
    {
      // User is signed in.
      console.log(user); 
      user.getIdToken().then(function(idToken)
      { // <------ Check this line
        console.log(idToken); // It shows the Firebase token now
      });
      console.log(user.uid);
      firebase.storage().ref('users').child(user.uid + "/designs").put(file);
    }
    else
    {
      // No user is signed in.
      console.log("state = definitely signed out");
    }
  });