title: NodeJS: What's the difference between a Duplex stream and a Transform stream?
body: <p>The <a href="http://nodejs.org/api/stream.html">Stream docs</a> state that <a href="http://nodejs.org/api/stream.html#stream_class_stream_duplex">Duplex Streams</a> "are streams that implement both the Readable and Writable interfaces" and <a href="http://nodejs.org/api/stream.html#stream_class_stream_transform">Transform Streams</a> "are Duplex streams where the output is in some way computed from the input." Unfortunately, the docs do not describe what Transform streams provide above and beyond Duplex streams.</p>
  
  <p>Are there any differences between the two? When would you use one over the other?</p>