javaScript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>