Creating transform streams

Streams allow for asynchronous programming. The most common stream is the transform stream; it's a black box that takes input and produces output asynchronously.

In this recipe, we'll look at creating a transform stream with the through2 module. In the There's more section, we'll look at how to create streams with the core stream module.

Getting ready

Let's create a folder called through-streams with an index.js, initialize the folder as a package, and install through2:

$ mkdir through-streams 
$ cd through-streams 
$ npm init -y 
$ npm install through2 
$ touch index.js

Note

Why the 2?The through2 module is a successor to the through module. The through module was built against an earlier Node core streams API (retrospectively called Streams 1 API). Later versions of Node introduced Streams 2 (and indeed 3). The through2 module was written to use the superior Streams 2 API (and is still relevant for the Streams 3 API; there's no need for a through3!). In fact, any...