W3School TIY
编辑您的代码：
<html> <body> <form id="form1"> <input type="radio" id="radio1" /> </form> <p>The form containing the radio button is: <script type="text/javascript"> x=document.getElementById('radio1'); document.write(x.form.id); </script></p> </body> </html>
查看结果: