JavaScript判断是刷新还是关闭？

window.onbeforeunload = function()

{

var n = window.event.screenX - window.screenLeft;

var b = n > document.documentElement.scrollWidth-20;

if(b && window.event.clientY < 0 || window.event.altKey)

{

alert("是关闭而非刷新");

window.event.returnValue = ""; //这里可以放置你想做的操作代码

}else{

alert("是刷新而非关闭");

}

}