title: Node.js proxy with ability to change response headers and inject additional request data
body: <p>I'm writing a node.js proxy server, serving requests to an API on different domain. </p>
  
  <p>I'd like to use <a href="https://github.com/nodejitsu/node-http-proxy" rel="nofollow noreferrer">node-http-proxy</a> and I have already found <a href="https://stackoverflow.com/questions/12755865/rewrite-response-headers-with-node-http-proxy">a way to modify response headers</a>. </p>
  
  <p>But is there a way to modify request data on condition (i.e. adding API key) and taking into account that there might be different methods request - <code>GET</code>, <code>POST</code>, <code>UPDATE</code>, <code>DELETE</code>? </p>
  
  <p>Or maybe I'm messing up the purpose of <a href="https://github.com/nodejitsu/node-http-proxy" rel="nofollow noreferrer">node-http-proxy</a> and there is something more suitable to my purpose?</p>