title: How to reference a variable inside a module.exports in Node.js
body: <p>I have a module written like below:</p>
  
  <pre><code>module.exports = {
      port: '1337',
      facebook: {
          clientID: '123456789',
          clientSecret: 'a1b2c3d4e5f6g7h8i9j0k',
          callbackURL: 'http://localhost:1337/oauth/facebook/callback'
      }
  };
  </code></pre>
  
  <p>What I would like to do is use the port variable in the callbackURL:</p>
  
  <pre><code>callbackURL: 'http://localhost:1337/oauth/facebook/callback'
  </code></pre>
  
  <p>I tried:</p>
  
  <pre><code>callbackURL: 'http://localhost:'+ this.port +'/oauth/facebook/callback'
  </code></pre>
  
  <p>but obviously that's not correct since the facebook is another object. So, can someone solve this one, and please any additional reading that you have (in terms of deeper understanding) is welcome.</p>