Chaining external asynchronous javascript calls

Question

I have some external JS code that needs to run asynchronously. The way I call it is I create a script inside an asynchronous function which I then attach to the rest of the scripts on the page like so..

<script type="text/javascript">
 (function() {
   var second = document.createElement('script'); 
   second.type = 'text/javascript'; 
   second.async = true;
   second.src =  "http://myserver.com/second.js";
   var scripts = document.getElementsByTagName('script')[0];    
   scripts.parentNode.insertBefore(second, scripts);
       })();
   </script>

Now suppose there was another script (first.js) which also needs to run asynchronously but it needs to run before this script (second.js), how can I chain them together to ensure first.js is already loaded when second.js runs?

Not sure if I should go with jQuery getScript or if there was a simpler way?

Some code examples based on what I provided would be greatly appreciated.