<form id="myForm">

<label id="myLabel" for="male">Male</label>

<input type="radio" name="sex" id="male" value="male"><br>

</form>

<p>点击“尝试一下”按钮返回 label 所属的表单的 id</p>

<p id="demo"></p>

<button onclick="myFunction()">尝试一下</button>

<script>

function myFunction(){

    var x = document.getElementById("myLabel").form.id;

    document.getElementById("demo").innerHTML=x;

}

</script>

​