鼠标滚动事件

注意区间值是 正负120

$(document).on('mousewheel DOMMouseScroll', onMouseScroll);
function onMouseScroll(e){
   e.preventDefault();
   var wheel = e.originalEvent.wheelDelta || -e.originalEvent.detail;
   var delta = Math.max(-1, Math.min(1, wheel) );
   if(delta<0){//向下滚动
      console.log('向下滚动');
      alert("向下滚动");
   }else{//向上滚动
      console.log('向上滚动');
      alert("向上滚动");
   }
}