duplexer

What is duplexer?

The `duplexer` npm package is a utility for creating a duplex (readable and writable) stream from two separate streams: a writable stream for writing to and a readable stream for reading from. This is particularly useful in scenarios where you need to treat two separate streams as a single duplex stream for piping data through a series of transformations or operations.

What are duplexer's main functionalities?

Creating a duplex stream from a writable and readable stream

This code demonstrates how to create a duplex stream using `duplexer` by combining a writable stream, which logs data it receives, and a readable stream, which emits a single piece of data. The resulting duplex stream can be used to read data emitted by the readable stream and write data to the writable stream.

const {Writable, Readable} = require('stream');
const duplexer = require('duplexer');

const writable = new Writable({
  write(chunk, encoding, callback) {
    console.log(`Writing: ${chunk.toString()}`);
    callback();
  }
});

const readable = new Readable({
  read(size) {
    this.push('Read data');
    this.push(null); // No more data
  }
});

const duplex = duplexer(writable, readable);
duplex.on('data', (data) => console.log(`Read from duplex: ${data.toString()}`));
duplex.write('Data to write');

Other packages similar to duplexer

duplexify

Similar to `duplexer`, `duplexify` allows for the creation of a duplex stream from a writable and a readable stream. However, `duplexify` provides additional features such as being able to set the readable or writable part asynchronously and handling backpressure more effectively.

through2

While `through2` is a thin wrapper around Node.js streams.Transform (making it easier to create transform streams), it shares the concept of manipulating data streams with `duplexer`. Unlike `duplexer`, `through2` is more focused on transforming data rather than combining streams into a duplex stream.

pumpify

Similar to `duplexer`, `pumpify` combines streams into a single duplex stream. The difference lies in `pumpify`'s ability to combine an arbitrary number of streams into one, effectively piping data through multiple transformations in a more flexible manner than `duplexer`.

README

duplexer

Creates a duplex stream

Taken from event-stream

duplex (writeStream, readStream)

Takes a writable stream and a readable stream and makes them appear as a readable writable stream.

It is assumed that the two streams are connected to each other in some way.

Example

var cp = require('child_process')
  , duplex = require('duplexer')
  , grep = cp.exec('grep Stream')

duplex(grep.stdin, grep.stdout)

Installation

npm install duplexer

Tests

npm test

Contributors

• Dominictarr
• Raynos
• samccone

MIT Licenced