How can I auto generate an ID with the data from a customer name and customer email field?

var Sdk = window.Sdk || {};

(function (){
this.BookingNameOnChange = function(executionContext){
var formContext = executionContext.getFormContext();

var uniqueID = formContext.getAttribute('new_bookingname').getValue();
var customerName = formContext.getAttribute('new_customername').getValue();
var customerEmail = formContext.getAttribute('new_customeremail').getValue();

if(uniqueID == null){
formContext.getAttribute('new_bookingname').setValue(customerName + '/' + customerEmail);
}
}
}).call(Sdk);

This is the function I am using. I would like to generate an id with the customer Name and customer Email combined. But It is not working and also not throwing any error.