In the through2 docs, it says:
A tiny wrapper around Node.js streams.Transform (Streams2/3) to avoid explicit subclassing noise.
What is meant by that? What is this "subclassing noise"?
2 Answers
In the through2 docs it also says (nowadays):
Since Node.js introduced Simplified Stream Construction, many uses of through2 have become redundant.
The example by Rezvan above would then become:
const { Transform } = require('stream'); return new Transform({ transform(chunk, encoding, cb) { // do some data transformation this.push(chunk); cb(); } }); Common implementation on transform stream looks like:
ES5 syntax
const { Transform } = require('stream'); const util = require('util'); function MyTransform(options) { if (!(this instanceof MyTransform)) return new MyTransform(options); Transform.call(this, options); } util.inherits(MyTransform, Transform); MyTransform.prototype._transform = function (chunk, enc, cb) { // do some data transformation this.push(chunk); cb(); }; ES6 syntax
const { Transform } = require('stream'); class MyTransform extends Transform { constructor(options) { super(options); } _transform(chunk, encoding, cb) { // do some data transformation this.push(chunk) cb() } } As you can see, to implement transform stream you have to write some boilerplate code, like extending Transform interface etc.
By using through2 you just write your transformation function. Profit.
