title: Express routing methods actual implementation - trying to understand Express' inner workings
body: <p>So, as the title suggests I am digging through the Express code to understand a little bit more about it.</p>
  
  <p>I have been using the framework for a couple of years now and I've got used to writing things such as <code>app.post(...)</code>, <code>app.get(...)</code></p>
  
  <p>Turns out there is no explicit declaration/definition of these methods within the Express code that is posted on Github. I guess they are implemented in an  arcane, functional, obscure-to-JS-beginners way in there somewhere.</p>
  
  <p>I would very much appreciate an explanation as to how this is done.</p>