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<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>