代码示例:(标识:hdom_select_id)
<html>
<body>

<form id="myForm">
<select id="mySelect">
  <option>Apple</option>
  <option>Pear</option>
  <option>Banana</option>
  <option>Orange</option>
</select>
</form>

<p>这个下拉列表的 id 是:
<script type="text/javascript">
document.write(document.getElementById("mySelect").id)
</script>
</p>

</body>
</html>
运行结果: