@justinbeckwith/duplexify

Turn a writeable and readable stream into a single streams2 duplex stream.

Compare to duplexify

This is a fork of duplexify. It does a few things different:

• Doesn't take a dependency on the user space ReadableStream npm module (this is smaller)
• Uses TypeScript for type safety

Installation

npm install @justinbeckwith/duplexify

Usage

Use duplexify(writable, readable, streamOptions) (or duplexify.obj(writable, readable) to create an object stream)

1const {duplexify} = require('@justinbeckwith/duplexify')
2
3// turn writableStream and readableStream into a single duplex stream
4const dup = duplexify(writableStream, readableStream)
5
6dup.write('hello world') // will write to writableStream
7dup.on('data', (data) => {
8  // will read from readableStream
9})

You can also set the readable and writable parts asynchronously

1const dup = duplexify()
2
3dup.write('hello world') // write will buffer until the writable
4                         // part has been set
5
6// wait a bit ...
7dup.setReadable(readableStream)
8
9// maybe wait some more?
10dup.setWritable(writableStream)

If you call setReadable or setWritable multiple times it will unregister the previous readable/writable stream. To disable the readable or writable part call setReadable or setWritable with null.

If the readable or writable streams emits an error or close it will destroy both streams and bubble up the event. You can also explicitly destroy the streams by calling dup.destroy(). The destroy method optionally takes an error object as argument, in which case the error is emitted as part of the error event.

1dup.on('error', (err) => {
2  console.log('readable or writable emitted an error - close will follow')
3})
4
5dup.on('close', () => {
6  console.log('the duplex stream is destroyed')
7})
8
9dup.destroy() // calls destroy on the readable and writable part (if present)

HTTP request example

Turn a node core http request into a duplex stream is as easy as

1const {duplexify} = require('duplexify')
2const http = require('http')
3
4const request = (opts) => {
5  const req = http.request(opts)
6  const dup = duplexify(req)
7  req.on('response', (res) => {
8    dup.setReadable(res)
9  })
10  return dup
11}
12
13const req = request({
14  method: 'GET',
15  host: 'www.google.com',
16  port: 80
17})
18
19req.end()
20req.pipe(process.stdout)

License

MIT