Acme.BookStore.HttpApi.Host/node_modules/through2/README.md

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# through2

[![NPM](https://nodei.co/npm/through2.png?downloads&downloadRank)](https://nodei.co/npm/through2/)

**A tiny wrapper around Node streams.Transform (Streams2) to avoid explicit subclassing noise**

Inspired by [Dominic Tarr](https://github.com/dominictarr)'s [through](https://github.com/dominictarr/through) in that it's so much easier to make a stream out of a function than it is to set up the prototype chain properly: `through(function (chunk) { ... })`.

Note: As 2.x.x this module starts using **Streams3** instead of Stream2. To continue using a Streams2 version use `npm install through2@0` to fetch the latest version of 0.x.x. More information about Streams2 vs Streams3 and recommendations see the article **[Why I don't use Node's core 'stream' module](http://r.va.gg/2014/06/why-i-dont-use-nodes-core-stream-module.html)**.

```js
fs.createReadStream('ex.txt')
  .pipe(through2(function (chunk, enc, callback) {
    for (var i = 0; i < chunk.length; i++)
      if (chunk[i] == 97)
        chunk[i] = 122 // swap 'a' for 'z'

    this.push(chunk)

    callback()
   }))
  .pipe(fs.createWriteStream('out.txt'))
  .on('finish', function () {
    doSomethingSpecial()
  })
```

Or object streams:

```js
var all = []

fs.createReadStream('data.csv')
  .pipe(csv2())
  .pipe(through2.obj(function (chunk, enc, callback) {
    var data = {
        name    : chunk[0]
      , address : chunk[3]
      , phone   : chunk[10]
    }
    this.push(data)

    callback()
  }))
  .on('data', function (data) {
    all.push(data)
  })
  .on('end', function () {
    doSomethingSpecial(all)
  })
```

Note that `through2.obj(fn)` is a convenience wrapper around `through2({ objectMode: true }, fn)`.

## API

<b><code>through2([ options, ] [ transformFunction ] [, flushFunction ])</code></b>

Consult the **[stream.Transform](http://nodejs.org/docs/latest/api/stream.html#stream_class_stream_transform)** documentation for the exact rules of the `transformFunction` (i.e. `this._transform`) and the optional `flushFunction` (i.e. `this._flush`).