[removed] and [removed] is not working in Firefox , Safari , Opera?

Question

In my chat application I need to get confirmation from user , when my application closes.

So I used the window.onbeforeunload for confirmation alert and

Answer 1

Here is the working solution for ie, firefox and chrome:

var myEvent = window.attachEvent || window.addEventListener;
var chkevent = window.attachEvent ? 'onbeforeunload' : 'beforeunload'; /// make IE7, IE8 compitable

            myEvent(chkevent, function(e) { // For >=IE7, Chrome, Firefox
                var confirmationMessage = 'Are you sure to leave the page?';  // a space
                (e || window.event).returnValue = confirmationMessage;
                return confirmationMessage;
            });