title: In Firebase, how do you update the displayName field of a user in Auth?
body: <p>I currently have a function that creates a user account. I'd like to be able to add a username field too, but I can't seem to figure out how to update that. I noticed in the Google console, that there is a displayName field that is set to null. I don't know how to change it. This is what I have:</p>
  
  <pre><code>function create(email, password, username) {
      firebase.auth().createUserWithEmailAndPassword(email, password).catch(function(error) {
          $timeout(function() {
              var errorCode = error.code;
              var errorMessage = error.message;
              console.log(errorCode.toUpperCase() + ":" + errorMessage);
          })
      });
      firebase.auth().onAuthStateChanged(function(user) {
          if (user) {
              $timeout(function() {
                  console.log("Success! Account Created!");
                  user.displayName = username; /* this doesn't work*/
              });
          } else {}
      });
  }
  </code></pre>