滚轮IE和Firefox的代码不一样：
IE是mousewheel事件，Firefox是DOMMouseScroll事件
事件属性，IE是event.wheelDelta，Firefox是event.detail
属性的方向值也不一样，IE向上滚 > 0，Firefox向下滚 > 0
- //滚轮放大或缩小，基于Prototype 1.6
- var scrollfunc = function(event) {
- var direct = 0;
- if (event.wheelDelta) {
- direct = event.wheelDelta > 0 ? 1 : -1;
- } else if (event.detail) {
- direct = event.detail < 0 ? 1 : -1;
- }
- zoom(direct);
- };
- Event.observe(document, 'mousewheel', scrollfunc);
- Event.observe(document, 'DOMMouseScroll', scrollfunc); //firefox
