Comments in javascript may begin with the characters // code example
Example 1: js comment
//This does not effect the code.
var something = "But this does effect the code!";
Example 2: comment out in javascript
<script type="text/javascript">
<!--
// This is a single line JavaScript comment
document.write("I have comments in my JavaScript code!");
//document.write("You can't see this!");
//-->
</script>