beforeunload

<!DOCTYPE html>
<html>
<head>
    <title>BeforeUnload Event Example</title>
    <script type="text/javascript" src="EventUtil.js"></script>
</head>
<body>
    <div id="myDiv">Try to navigate away from this page.</div>
    <script type="text/javascript">
        EventUtil.addHandler(window, "beforeunload", function(event){
            event = EventUtil.getEvent(event);
            var message = "I'm really going to miss you if you go.";
            event.returnValue = message;
            return message;
        });

    </script>
</body>
</html>
【推广】 免费学中医，健康全家人
原文地址：https://www.cnblogs.com/human/p/3471356.html