asp.net关闭网页前触发js事件清空cookie

window.onbeforeunload = function () {
delCookie("CookieName");
}
//删除cookies
function delCookie(name) {
var exp = new Date();
exp.setTime(exp.getTime() - 1);
var cval = getCookie(name);
if (cval != null)
document.cookie = name + "=" + cval + ";expires=" + exp.toGMTString();
}

function getCookie(name) {
var arr, reg = new RegExp("(^| )" + name + "=([^;]*)(;|$)");
if (arr = document.cookie.match(reg))
return (arr[2]);
else
return null;
}