<!DOCTYPE html>
<html>

<head>
    <meta charset="UTF-8">
    <style type="text/css">
       /* 填写样式 */
       div{
        width:100px;
        height:100px;
        border-radius:50px;
        border:1px solid black
       }
    </style>
</head>

<body>
  <div></div> 
    <script type="text/javascript">
        /* 填写JavaScript */
        
    </script>
</body>

</html>