判断页面关闭和刷新

[fermity_zyx]

 
    window.onbeforeunload = onbeforeunload_handler;
    function onbeforeunload_handler() {
    var x = window.event.clientX;
    var y = window.event.clientY;
     if (windows.event.clientX > document.body.clientWidth && windows.event.clientY < 0 || windows.event.altKey){
            alert("关闭");
            }
     else{
        alert("刷新");
        }
       
    }

网上找到的代码，X和Y显示undefined，是哪里错了么

[潮起潮落]

http://www.w3school.com.cn/tiy/t.asp?f=hdom_event_clientx