auth_firebase_database.js

//Firebase Auth instance
const auth = firebase.auth();
//Firebase Database instance
const database = firebase.database();

//get all input element as an array
var formData = formToArray('signUp');

const email = formData.email_address;
const password = formData.password;

const promise = auth.createUserWithEmailAndPassword(email, password);
promise.then(function (user) {
   // get the current loggeg in users details
   console.log(user);
   saveCreatedAccount(formData, user, email);
})
promise.catch(function(error) {
  // Handle Errors here.
  var errorCode = error.code;
  var errorMessage = error.message;
  // ...
});

function saveCreatedAccount(formData, user, email) {
   // the unique id from the saved user
   var node_id = user.user.uid;

   formData.node_id = node_id;                // generated UId by firebase
   formData.email = email;                    // emaill address
   formData.type = 'password';                // the type of which the account was created
   formData.created = new Date().valueOf();   // Current time inwhich the account was created

   //save new user to data
   writeUserData(node_id, formData);
}

function writeUserData(node_id, formData) {
      database.ref('users/' + node_id).set(formData, function (error) {
          if (error) {
              showAlert(error);
              showLoading('false', 'div_holder');
          } else {
              showAlert(node_id+' Saved. Please login', 1);
              showLoading('false', 'div_holder');
          }
      });
  }