JS: Determine Scroll Direction

gistfile1

function init_scroll(event, delta) {
   var deltaOfInterest = delta,
   timeNow = new Date().getTime(),
   quietPeriod = 500;
   
   // Cancel scroll if currently animating or within quiet period
   if(timeNow - lastAnimation < quietPeriod + settings.animationTime) {
      event.preventDefault();
      return;
   }

   if (deltaOfInterest < 0) {
      //el.moveDown()
   } else {
      //el.moveUp()
   }
   lastAnimation = timeNow;
}

$(document).bind('mousewheel DOMMouseScroll', function(event) {
   event.preventDefault();
   var delta = event.originalEvent.wheelDelta || -event.originalEvent.detail;
   init_scroll(event, delta);
});