title: javascript adding a value to function arguments
body: <p>I'm trying to add an argument to a function passed along as an argument in an express js route.</p>
  
  <p>This is an expressjs route:</p>
  
  <pre><code>app.get('path', someFunc,
  function(req, res, next) {
    res.render('layout');
  });
  </code></pre>
  
  <p>The function someFunc right there takes the arguments req, res, next.</p>
  
  <p>I want to add an additional argument to it. If I use apply or call it seems to replace all the existing arguments.</p>
  
  <p>I want to be able to do:</p>
  
  <pre><code>someFunction (req, res, next, custom) {}
  </code></pre>
  
  <p>How can I do this? Thanks.</p>