code: function getScript(url, async, cb) {
      if (typeof async === 'function') {
        cb = async;
        async = false;
      }
  
      var el = document.createElement('script');
  
      // Script attributes
      el.type = 'text/javascript';
      el.src = url;
  
      // Should the script be loaded asynchronously?
      if (async)
        el.async = true;
  
      // Defining callbacks
      el.onload = el.onreadystatechange = function() {
        if ((!this.readyState ||
              this.readyState == 'loaded' ||
              this.readyState == 'complete')) {
          el.onload = el.onreadystatechange = null;
  
          // Removing element from head
          artoo.mountNode.removeChild(el);
  
          if (typeof cb === 'function')
            cb();
        }
      };
  
      // Appending the script to head
      artoo.mountNode.appendChild(el);
    }
docs: Loading an external file the same way the browser would load it from page