title: View Express JS response headers?
body: <p>If I need to see the incoming request headers I use: <code>req.headers</code>.</p>
  
  <p>I need to see the list of all headers that will be in the response.</p>
  
  <p><code>res.headers</code> is <code>undefined</code>.</p>
  
  <p>I know I can set response headers: <code>res.header('', '')</code>.</p>
  
  <p>How do I view the response headers..?</p>