Javascript 鼠标滚轮方向判断

// firefox
if(Element.addEventListener){
    Element.addEventListener('DOMMouseScroll', function(event){
        console.log(event.detail); //Firefox使用detail，取值±3
    }, false);
}

// ie & chrome & opera & safari
Element.onmousewheel = function(event) {
    event = event || window.event;
　　console.log(event.wheelDelta); //IE、Opera、Safari、Firefox、Chrome使用wheelDelta，取值±200

 };