Jquery Form Warn

gistfile1.js

(function(js) {
    js(document).ready(function() {

        js('form[data-warn]').each(function(index, element) {
            js(element).data('content', js(element).serialize());
        });

        js(window).on('beforeunload', function(){
            var changed = false;
            js('form[data-warn]').each(function(index, element) {
                if(false === changed) {
                    changed = (
                        js(element).data('content') !== js(element).serialize()
                    );
                }
            });
            return (true === changed) ? 'Are you sure?' : null;
        });

    });
}(jQuery));