title: Extend JavaScript Class from separate file
body: <p>I'm sorry to ask quite a dim question as I'm very new to OOP in JavaScript. </p>
  
  <p>I'm trying to use <a href="http://ejohn.org/blog/simple-javascript-inheritance/" rel="nofollow">John Resig's Simple JavaScript Inheritance method</a>, and ideally I'd like to store this within say <code>utils.js</code>, and then use it (using <code>Class.extend</code>), throughout the range of script files that my project uses. Is this possible? I've noticed that if I create a subclass from within my <code>utils.js</code> file, I can then create a <code>new</code> instance of that class from a different script, so that makes me think it might be possible. Does it have something to do with the method being wrapped in an immediately-invoked function expression? </p>