how to identify onbeforeunload was caused by clicking close button

Question

How do I determine if onbeforeunload was caused by clicking the close button or a page refresh or generally what event caused onbeforeunload?

here is a snippet:

window.onbeforeunload = function( e ){
    if( !e ) e = window.event;

    // insert code to determine which is the source of the event
}

Please help me.

Answer 1

As far as I know, there is no way of determining what caused the onbeforeunload. The event is triggered when window is about to close whether closing the browser or some other way.

Answer 2

If the close button was pressed the value of e.clientY is negative. For the other possible sources i doubt there is a solution.

window.onbeforeunload = function() {
   var e = window.event;
   alert(e.clientX + " / " + e.clientY);
}