jQuery UI Dialog OnBeforeUnload
The correct way to display the alert is to simply return a string. Don't call the alert() method yourself.
<script type="text/javascript"> $(window).on('beforeunload', function() { if (iWantTo) { return 'you are an idiot!'; } }); </script>See also: https://developer.mozilla.org/en-US/docs/Web/Events/beforeunload
You can also make an exception for leaving the page via submitting a particular form:
$(window).bind('beforeunload', function(){ return "Do you really want to leave now?";});$("#form_id").submit(function(){ $(window).unbind("beforeunload");});
this works for me
$(window).bind('beforeunload', function() { return 'Do you really want to leave?' ;});