NodeJS: What's the difference between a Duplex stream and a Transform stream?

Question

The Stream docs state that Duplex Streams \"are streams that implement both the Readable and Writable interfaces\" and Transform Streams \"are Duplex streams where the outpu

Answer 1

A Duplex stream can be thought of a readable stream with a writable stream. Both are independent and each have separate internal buffer. The reads and writes events happen independently.

                             Duplex Stream
                          ------------------|
                    Read  <-----               External Source
            You           ------------------|   
                    Write ----->               External Sink
                          ------------------|
            You don't get what you write. It is sent to another source.

A Transform stream is a duplex where the read and write takes place in a causal way. The end points of the duplex stream are linked via some transform. Read requires write to have occurred.

                                 Transform Stream
                           --------------|--------------
            You     Write  ---->                   ---->  Read  You
                           --------------|--------------
            You write something, it is transformed, then you read something.