Wheel events is compatible with Firefox

     var wrap = document.querySelector("#wrap");
	 
	 if(wrap.addEventListener){
		wrap.addEventListener("DOMMouseScroll",fn);
	 }
	 wrap.onmousewheel=fn;
	 function fn(ev){
		ev = ev||event;    
		var stat = "";
		//非火狐浏览器
		if(ev.detail){
			stat = ev.detail<0?"up":"down";
		}
		//火狐浏览器
		if(ev.wheelDalta){
			stat = ev.wheelDalta>0?"up":"down";		
		}
		switch(stat){
		case "up":
			//滚轮往上滑
			break;
		case "down":
			//滚轮往下滑
			break;
		}
/*
		if(ev.preventDefault){  //禁用事件的默认行为dom2
			ev.preventDefault();
		}
		return false;           //禁用事件的默认行为dom0
*/
	 }