Tryit Editor v2.9

Edit This Code:
<!DOCTYPE html>
<html>
<body>

Checkbox: <input type="checkbox" id="myCheck">

<p>Click the "Try it" button to disable the checkbox.</p>

<button onclick="myFunction()">Try it</button>

<script>
function myFunction() {
    document.getElementById("myCheck").disabled = true;
}
</script>

</body>
</html>