code: function(event) {
            var e = event || window.event;
            JSEvents.fillMouseEventData(JSEvents.wheelEvent, e, target);
            HEAPF64[(((JSEvents.wheelEvent)+(72))>>3)]=e["deltaX"];
            HEAPF64[(((JSEvents.wheelEvent)+(80))>>3)]=e["deltaY"];
            HEAPF64[(((JSEvents.wheelEvent)+(88))>>3)]=e["deltaZ"];
            HEAP32[(((JSEvents.wheelEvent)+(96))>>2)]=e["deltaMode"];
            var shouldCancel = Module['dynCall_iiii'](callbackfunc, eventTypeId, JSEvents.wheelEvent, userData);
            if (shouldCancel) {
              e.preventDefault();
            }
          }
docs: The DOM Level 3 events spec event 'wheel'