<!DOCTYPE html>
<html>
<body>
<p>Click the button to create, and add, a comment to the HTML document.</p>
<button onclick="myFunction()">Try it</button>
<p id="demo"></p>
<script>
function myFunction() {
var c = document.createComment("My personal comments");
document.body.appendChild(c);
var x = document.getElementById("demo");
x.innerHTML = "A comment was added to this document, but as you know, comments are invisible.";
}
</script>
</body>
</html>