add script to head using javascript code example

Example 1: how to add script in html head

<script src="script.js" defer></script>

<!--just add defer attribute so script will execute at last-->

Example 2: javascript add script in head programmatically

var my_awesome_script = document.createElement('script');

my_awesome_script.setAttribute('src','http://example.com/site.js');

document.head.appendChild(my_awesome_script);