var inputField = document.getElementById('inputField');
var myName = document.getElementById('myName');

var config = {
  apiKey: "AIzaSyBFvYXH1TlMDkmuRMXQCkogUec505eXp-I",
  authDomain: "scrimba-test.firebaseapp.com",
  databaseURL: "https://scrimba-test.firebaseio.com",
  storageBucket: "scrimba-test.appspot.com",
  messagingSenderId: "475284881865"
};
firebase.initializeApp(config);

var user = firebase.database().ref('users/123');

inputField.onkeyup = function(event) {
  user.set({
    name: event.target.value
  });
}

user.on('value', function(snapshot) {
  myName.innerText = snapshot.val().name;
});