jQuery beforeunload and areYouSure jquery plugin

Question

I found that we can use two commonly used functions to stop propagating before leaving the unsaved data

• beforeunload
• areYouSure - jquery plugin

Both of the above can be used. following is the minor code i tested

 <script>
 $(function() {

    $('#form').data('serialize',$('#form').serialize()); // On load save form current state

    $(window).bind('beforeunload', function(e){                       // binding the beforeunload
        if($('#form').serialize()!= $('#form').data('serialize'))
            return true; 
        else 
            e=null; // i.e; if form state change show warning box, else don't show it.
    });

</script>

Note: i am unbinding the function for save button to hide the warning same code i tested for areYouSure

so now my question is, am i following the correct approach, and which one is better efficiency wise ?