duplexer2 example for node 4.x

example.js

#!/usr/bin/env node

"use strict";

const stream = require("readable-stream");

const duplexer2 = require("duplexer2");

const writable = new class extends stream.Writable {
  constructor() {
    super({objectMode: true})
  }
  _write(input, encoding, done) {
    if (readable.push(input)) {
      return done();
    } else {
      readable.once("drain", done);
    }
  }
};

const readable = new class extends stream.Readable {
  constructor() {
    super({objectMode: true})
  }
  _read() {
    // no-op
  }
};

// simulate the readable thing closing after a bit
writable.once("finish", () => {
  setTimeout(() => {
    readable.push(null);
  }, 500);
});

var duplex = duplexer2(writable, readable);

duplex.on("data", e => {
  console.log("got data", JSON.stringify(e));
});

duplex.on("finish", () => {
  console.log("got finish event");
});

duplex.on("end", () => {
  console.log("got end event");
});

duplex.write("oh, hi there", () => {
  console.log("finished writing");
});

duplex.end(() => {
  console.log("finished ending");
});