mouseweel兼容火狐

<div id="box" style="width:500px;height:300px;background-color:#ccc;overflow:auto;">    <div style="height:500px;"></div></div><script type="text/javascript">var isFirefox = /Firefox/i.test(navigator.userAgent); //判断是不是火狐浏览器var mwEvent = !isFirefox ? 'mousewheel' : 'DOMMouseScroll'; //是火狐浏览器用DOMMouseScrolldocument.getElementById('box').addEventListener(mwEvent, function(event) {    console.dir(2); });</script>