js 禁止鼠标滚动

window.onload=function(){
var oDiv=document.getElementById("top");

oDiv.onmouseover = function () {
if(window.event){
document.onmousewheel = function () {
window.event.returnValue="false";
return false;
}
}else{
oDiv.addEventListener("DOMMouseScroll",function(ev){ev.preventDefault();} , false);
}

};

oDiv.onmouseout=function(){
document.onmousewheel=null;
}

}