js 判斷web頁面關閉、刷新、跳轉

window.onbeforeunload = function(){
    if(document.all){ //ie
        //右上角關閉按鈕 或 alt+F4 或 ctrl+w
        if(event.clientX > document.body.clientWidth || event.clientY < 0 ||event.altKey || event.ctrlKey){
            return "關閉窗口";
        }else{
            return "刷新或跳轉";
        }
    }else{
        return "刷新、跳轉、關閉";
    }
}