JS捕获窗口关闭事件

<script type="text/javascript">  

    window.onbeforeunload = onbeforeunload_handler;  
    window.onunload = onunload_handler;  

    function onbeforeunload_handler(){  

        var warning="确认退出?";          

        return warning;  

    }  
      
    function onunload_handler(){  

        var warning="谢谢光临";  

        alert(warning);  

    }  
</script>

window.onbeforeunload = onbeforeunload_handler;  
    window.onunload = onunload_handler;  

这两种都可以捕获窗口关闭事件，window.onbeforeunload 在window.onunload之前执行