JS 判断鼠标滚轮的上下滚动

<script type="text/javascript">          var scrollFunc = function (e) {          e = e || window.event;          if (e.wheelDelta) {  //判断浏览器IE，谷歌滑轮事件                           if (e.wheelDelta > 0) { //当滑轮向上滚动时                  alert("滑轮向上滚动");              }              if (e.wheelDelta < 0) { //当滑轮向下滚动时                  alert("滑轮向下滚动");              }          } else if (e.detail) {  //Firefox滑轮事件              if (e.detail> 0) { //当滑轮向上滚动时                  alert("滑轮向上滚动");              }              if (e.detail< 0) { //当滑轮向下滚动时                  alert("滑轮向下滚动");              }          }      }      //给页面绑定滑轮滚动事件      if (document.addEventListener) {//firefox          document.addEventListener('DOMMouseScroll', scrollFunc, false);      }      //滚动滑轮触发scrollFunc方法  //ie 谷歌      window.onmousewheel = document.onmousewheel = scrollFunc;       </script>