Sign Up for Free

RunKit +

Try any Node.js package right in your browser

This is a playground to test code. It runs a full Node.js environment and already has all of npm’s 400,000 packages pre-installed, including through with all npm packages installed. Try it out:

var through = require("through")

This service is provided by RunKit and is not affiliated with npm, Inc or the package authors.

through v2.3.8

simplified stream construction


build status testling badge

Easy way to create a Stream that is both readable and writable.

  • Pass in optional write and end methods.
  • through takes care of pause/resume logic if you use this.queue(data) instead of this.emit('data', data).
  • Use this.pause() and this.resume() to manage flow.
  • Check this.paused to see current flow state. (write always returns !this.paused).

This function is the basis for most of the synchronous streams in event-stream.

var through = require('through')

through(function write(data) {
    this.queue(data) //data *must* not be null
  function end () { //optional

Or, can also be used without buffering on pause, use this.emit('data', data), and this.emit('end')

var through = require('through')

through(function write(data) {
    this.emit('data', data)
  function end () { //optional

Extended Options

You will probably not need these 99% of the time.


By default, through emits close when the writable and readable side of the stream has ended. If that is not desired, set autoDestroy=false.

var through = require('through')

//like this
var ts = through(write, end, {autoDestroy: false})
//or like this
var ts = through(write, end)
ts.autoDestroy = false


MIT / Apache2

RunKit is a free, in-browser JavaScript dev environment for prototyping Node.js code, with every npm package installed. Sign up to share your code.
Sign Up for Free