title: Double underscore in front of a variable
body: <p>I have the following code snippet in my node code. </p>
  
  <pre><code>var fs = require('fs');
  
  fs.readdir(__dirname, function (err, files) {
      console.log(files);
  });
  </code></pre>
  
  <p>Why does the variable '__dirname' have double underscores?
  I know that one underscore is a naming convention for a private/protected variable... but does double underscore mean something more?</p>