Node.js "res is not defined"
<p>What Javascript do I add to define res?  Thanks!</p>

<p>Error message:</p>

<blockquote>
  <p>ReferenceError: res is not defined</p>
</blockquote>

<p>Code:</p>

<pre><code>app.get('/', function(request, response) {
    res.sendFile(path.join(__dirname, '/public', 'index.html'));
})
</code></pre>