how to comment out javascript block of code 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>