<!DOCTYPE html>
<html>
<body>
<form>
First Name: <input type="text" id="fname" value="Donald">
Convert to upper case
<input type="radio" onclick="if(this.checked){myFunction()}">
</form>
<script>
function myFunction() {
document.getElementById("fname").value = document.getElementById("fname").value.toUpperCase();
}
</script>
</body>
</html>