Swype Web Script

Witam.
Aktualnie jestem w trakcie analizowania problemu, czemu mi nie działa dany skrypt.

<script type="text/javascript">
        
        /* -------------------------------------------------------------------
        /* --- FUNCTION SWIPE WEB / Przesuwanie palcem po stronie ---
        ------------------------------------------------------------------- */
         
        window.addEventListener('load', function(){
        
            var el = document.getElementById('site_container');
            var touchsurface = el;
            var swipedir;
            var startX;
            var startY;
            var distX;
            var distY;
            var threshold = 150;
            var restraint = 100;
            var allowedTime = 300;
            var elapsedTime;
            var startTime;
            var handleswipe = callback || function(swipedir){};
         
            touchsurface.addEventListener('touchstart', function(e){
                var touchobj = e.changedTouches[0];
                swipedir = 'none';
                var dist = 0;
                startX = touchobj.pageX;
                startY = touchobj.pageY;
                startTime = new Date().getTime();
                e.preventDefault();
            }, false);
         
            touchsurface.addEventListener('touchmove', function(e){
                e.preventDefault();
            }, false)
         
            touchsurface.addEventListener('touchend', function(e){
                var touchobj = e.changedTouches[0];
                distX = touchobj.pageX - startX;
                distY = touchobj.pageY - startY;
                elapsedTime = new Date().getTime() - startTime;
                if (elapsedTime <= allowedTime){
                    if (Math.abs(distX) >= threshold && Math.abs(distY) <= restraint){
                        swipedir = (distX < 0)? 'left' : 'right';
                    }
                    else if (Math.abs(distY) >= threshold && Math.abs(distX) <= restraint){
                        swipedir = (distY < 0)? 'up' : 'down';
                    }
                }
                handleswipe(swipedir);
                e.preventDefault();
            }, false);
            
            swipedetect(el, function(swipedir){
                //swipedir contains either "none", "left", "right", "top", or "down"
                if (swipedir =='left') {
                    alert('You just swiped left!');
                } else if (swipedir == 'right') {
                    alert('You just swiped right!');
                }
            })
         
        }, false);
</script>

Skrypt używam na stronie TUMBLR'a do otwierania i zamykania bocznego menu stworzonego przez CSS...
Ogólnie skrypt w ogóle mi nie wyrzuca mi żadnego alertu. Cała strona jest oznaczona przez "site_container", a reszta skryptu która mi działa na przycisk to:

<script>
        function openNav() {
            document.getElementById("sidebar_nav").style.left           =   "0px";
            //document.getElementById("site_container").style.marginLeft  =   "400px";
            document.getElementById("button_menu").onclick              =   closeNav;
        }
        
        function closeNav() {
            document.getElementById("sidebar_nav").style.left           =   "-400px";
            //document.getElementById("site_container").style.marginLeft  =   "0px";
            document.getElementById("button_menu").onclick              =   openNav;
        }
        </script>

I on działa!