Add another data to the firebase database

In my web app, I want to create a classroom and add the data to my firebase database.

var fbclass = firebase.database().ref().child('Classes');

function classcreation(q) {

  var usuid = generateId();
  var myClasses={};

  myClasses.TheClass = document.getElementById('classroomName').value;
  myClasses.Teacher = user.displayName;
  myClasses.TeacherEmail = user.email;
  myClasses.ClassID = usuid;
  fbclass.child(user.uid).set(myClasses);
  }

function generateId(){
return 'xxxx-xxxx-xxxx'.replace(/[x]/g, function(){
  return (Math.random() * 9 | 0 ).toString();
  })
}

After submitting the button it will then store the data to the firebase

IMG 1

but the problem is, if I create another classroom with the same user, it will just update the TheClass[classname] and not create another classroom.

IMG

What's wrong with my code? What did I miss?