javascrpt监听窗口关闭

<script type="text/javascript">       window.onbeforeunload = function(e) {           e = e || window.event;           var msg = "您确定要离开此页面吗？";
// IE           e.cancelBubble = true;           e.returnValue = msg;
// Firefox           if(e.stopPropagation) {              e.stopPropagation();              e.preventDefault();           }
// Chrome / Safari           return msg;         };</script>

[javascript] view plaincopywindow.addEventListener("beforeunload", function( event ) {
event.returnValue = "\o/";}
);
//is equivalent to
window.addEventListener("beforeunload", function( event ) {
event.preventDefault();
});

<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>