Call Javascript from PHP for Wordpress post.

What I want to do is to state that if my page ID for wordpress is #ID a java script will work. I have little knowledge of PHP but that is what i want it to do...

<?php if(is_single('123')) echo Javascript here 

PHP:

How do I do it ? Help highly appreciated.

 

<?php
if(is_single('123'))
{
?>
<script>
execute(aaa,aaa);
</script>
<?php
}
?>