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<!DOCTYPE html> <html> <body> Radio button: <input type="radio" name="colors" id="myRadio" checked> <p>Click the "Try it" button to find out if the radio button is checked by default.</p> <button onclick="myFunction()">Try it</button> <p id="demo"></p> <script> function myFunction() { var x = document.getElementById("myRadio").checked; document.getElementById("demo").innerHTML = x; } </script> </body> </html>