判断浏览器是刷新还是关闭

[code lang=”js”]

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 = "是否关闭？";
}else{
// alert("是刷新而非关闭");
if(document.getElementById(‘content’).value!=”){
window.event.returnValue = ‘刷新后将丢失现有的日记内容，确认刷新？’;
}
}
}

[/code]