HTML

onchange js

<script>
document.getElementById("fname").addEventListener("change", myFunction);

function myFunction() {
  var x = document.getElementById("fname");
  x.value = x.value.toUpperCase();
}
</script>

onchange html

<element onchange="myFunction()"> 
<!--Runs JS function when html element is changed. Example:-->
<select onchange="console.log("Changed")">
<!-- Outputs "Changed" when select element option is changed! -->