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;
        }