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>