I\'m using Firebase and I\'m trying to add a username to the database with the email and password.
You need to create that database users
child node yourself ;-)
The createUserWithEmailAndPassword
function only creates a new user in Firebase authentication service. The database itself isn't changed at all as a result.
To add this new user to the database as well, try:
firebase.database().ref("users").child(user.uid).set(...)