As RyanDev has already mentioned calEvent is not a built-in function, and that is why you just cannot call the id member, because it is
undefined.
What you might try to do is, to check for which event was clicked. You can make a good use of the
this
keyword in jQuery to run the code over the object that raised the event. Think of your code like this,
$('#btnPopupDelete').click(function () {
var id = $(this).attr('id');
DeleteEvent(id);
});
Now, suppose if the ID of your button was the ID of the event to be deleted, then this code would pass the value of the ID attribute of the button and the event would be deleted.