How Can I Prevent A Page Unload With Jquery?

In my program, if a user tries to leave a page, he'll receive a dialog box asking if he is sure he wants to leave. How should I implement the 'cancel' option if the user chooses no

Solution 1:

window.onbeforeunload = function() {
    return'You have unsaved changes!';
}

many question about this in stackoverflow How can I override the OnBeforeUnload dialog and replace it with my own?

JavaScript + onbeforeunload

Solution 2:

 jQuery(window).on('beforeunload',function(){
    var value = navigateAway(isDirty);
    if(value=="changed")`enter code here`
    {
        if(jQuery("#saveCheck").val()=="false")
        {
            return "<?phpecho JText::_('OVR_WANT_TO_LEAVE');?>";
        }
    }

 });