​x
 
<html>
<body>
​
<form id="myForm">
<select id="mySelect">
  <option>苹果</option>
  <option>桃子</option>
  <option>香蕉</option>
  <option>桔子</option>
</select>
</form>
​
<p>该表单的 id 是：
<script type="text/javascript">
document.write(document.getElementById("mySelect").form.id)
</script>
</p>
​
</body>
</html>
​