關閉瀏覽器事件

<script type="text/javascript">
    window.onbeforeunload = function() {

        var n = window.event.screenX - window.screenLeft;
        var b = n > document.documentElement.scrollWidth - 20;
       
        //用戶點擊瀏覽器右上角關閉按鈕
        if (b && window.event.clientY < 0 || event.clientX > document.body.clientWidth && event.clientY < 0 || event.altKey) {

            window.event.returnValue = "確定要退出本頁嗎?";
            window.location.href = "";
        }
        //用戶點擊任務欄，右鍵關閉
        else if (event.clientY > document.body.clientHeight || event.altKey) {
           
            window.event.returnValue = "確定要退出本頁嗎?";
        }      
        else//其他情況爲刷新  
        {
            alert("你在刷新");
        }
    }
</script>