Tryit Editor v2.9

Edit This Code:
<!DOCTYPE html>
<html>
<body>

<form id="form1">
<button id="btn1" type="button">HTML</button>
</form>

<p>Click the "Try it" button to display the id of the form the HTML button belongs to:</p>

<button onclick="myFunction()">Try it</button>

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

<script>
function myFunction() {
    var x = document.getElementById("btn1").form.id;
    document.getElementById("demo").innerHTML = x;
}
</script>

</body>
</html>