Automatic codebox with copy and download button

Now it would automatically change by default all your codeboxes to this type. No need to add any extra syntax or anything !!
<!--[Demo]-->

<script>

	var a = document.getElementsByClassName('copy-btn');

	for (let i = 0; i < a.length; i++) {

		a[i].addEventListener('click', function () {

			var b = a[i].getAttribute("name");

			var text = document.getElementById(b);

			text.select();

			document.execCommand('copy');

		});

	}

</script>