js给页面添加滚动事件并判断滚动方向

<script>
   var scrollFunc = function (e) {
        var direct = 0;
        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");
            }
        }
        ScrollText(direct);
    }
    //给页面绑定滑轮滚动事件
    if (document.addEventListener) {
        document.addEventListener(‘DOMMouseScroll‘, scrollFunc, false);
    }
    //滚动滑轮触发scrollFunc方法
    window.onmousewheel = document.onmousewheel = scrollFunc;  
</script>