Drupal: How to use the Context Module to include javascript on specific pages

I needed a solution which allowed me to include Optimizely’s A/B testing snippet on certain pages, and have the ability to change those page rules without modifying code.

I do this using the Context module, I apply a class to the body for a node with the path “demo”, like so:

Then, in html.tpl.php, in the <head> of my document, I have the following code:

<?php 
  if (!empty($classes)) {
    if (strpos($classes, 'has-optimizely') !== false) {
      print '<script src="https://cdn.optimizely.com/js/xxxx.js"></script>';
    }
  }
?>

<?php

if (!empty($classes)) {

if (strpos($classes, 'has-optimizely') !== false) {

print '<script src="https://cdn.optimizely.com/js/xxxx.js"></script>';

}