<form id="myForm">

<input type="week" id="myWeek">

</form>

<p>点击按钮返回week 字段所属的表单id</p>

<button onclick="myFunction()">点我</button>

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

<script>

function myFunction() {

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

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

}

</script>

​