Like duplexer but using streams3


Like duplexer but using Streams3

var stream = require("stream");
var duplexer2 = require("duplexer2");
var writable = new stream.Writable({objectMode: true}),
    readable = new stream.Readable({objectMode: true});
writable._write = function _write(inputencodingdone) {
  if (readable.push(input)) {
    return done();
  } else {
    readable.once("drain", done);
readable._read = function _read(n) {
  // no-op 
// simulate the readable thing closing after a bit 
writable.once("finish", function() {
  setTimeout(function() {
  }, 500);
var duplex = duplexer2(writable, readable);
duplex.on("data", function(e) {
  console.log("got data", JSON.stringify(e));
duplex.on("finish", function() {
  console.log("got finish event");
duplex.on("end", function() {
  console.log("got end event");
duplex.write("oh, hi there", function() {
  console.log("finished writing");
duplex.end(function() {
  console.log("finished ending");
got data "oh, hi there"
finished writing
got finish event
finished ending
got end event

This is a reimplementation of duplexer using the Streams3 API which is standard in Node as of v4. Everything largely works the same.

Available via npm:

$ npm i duplexer2

Creates a new DuplexWrapper object, which is the actual class that implements most of the fun stuff. All that fun stuff is hidden. DON'T LOOK.

duplexer2([options], writable, readable)
const duplex = duplexer2(new stream.Writable(), new stream.Readable());


  • options - an object specifying the regular stream.Duplex options, as well as the properties described below.
  • writable - a writable stream
  • readable - a readable stream


  • bubbleErrors - a boolean value that specifies whether to bubble errors from the underlying readable/writable streams. Default is true.

3-clause BSD. A copy is included with the source.