Tryit Editor v2.9

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

<h3>A demonstration of how to access a File Upload Button</h3>

<input type="file" id="myFile">

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

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

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

</body>
</html>