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