auth.js

//Firebase Auth instance
const auth = firebase.auth();
const email = fornData.email_address;
const password = fornData.password;

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