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<!DOCTYPE html> <html> <body> <form id="myForm"> <fieldset id="myFieldset"> <legend>Personalia:</legend> Name: <input type="text"><br> Email: <input type="text"><br> Date of birth: <input type="text"> </fieldset> </form> <p>Click the button to display the id of the form the fieldset belongs to.</p> <button onclick="myFunction()">Try it</button> <p id="demo"></p> <script> function myFunction() { var x = document.getElementById("myFieldset").form.id; document.getElementById("demo").innerHTML = x; } </script> </body> </html>