菜鸟教程在线编辑器

 
                <!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"> 
<title>菜鸟教程(runoob.com)</title> 
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.0.0/jquery.min.js">
</script>
<script>
$(document).ready(function(){
  $(window).unload(function(){
    alert("Goodbye!");
  });
});
</script>
</head>
<body>

<p>当你点击 <a href="https://www.runoob.com">这个链接</a>, 或者关闭窗口，alert 窗口会弹出。</p>
</body>
</html>
              