改变下来列表选项的可见数目 - 在线编辑器

          <!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>蜜蜂教程(mifengjc.com)</title>
  <script>
    function displayResult() {
      document.getElementById("mySelect").size = 4;
    }
  </script>
</head>
<body>

  <form>
    <select id="mySelect">
  <option>Apple</option>
  <option>Pear</option>
  <option>Banana</option>
  <option>Orange</option>
</select>
  </form>
  <button type="button" onclick="displayResult()">修改大小</button>

</body>
</html>
        