title: Why should I reference jQuery in a self contained function?
body: <pre><code>(function ($, undefined) {
  
      . . .
  
  })(jQuery);
  </code></pre>
  
  <p>I see this everywhere, but I don't understand why we're sending jQuery as a parameter in a self contained function. jQuery is already being referenced. Also, why are we defining <code>undefined</code> as a parameter?</p>