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>