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# from2 [](https://flattr.com/submit/auto?user_id=hughskennedy&url=http://github.com/hughsk/from2&title=from2&description=hughsk/from2%20on%20GitHub&language=en_GB&tags=flattr,github,javascript&category=software)[](http://github.com/hughsk/stability-badges) # `from2` is a high-level module for creating readable streams that properly handle backpressure. Convience wrapper for [readable-stream](http://github.com/isaacs/readable-stream)'s `ReadableStream` base class, with an API lifted from [from](http://github.com/dominictarr/from) and [through2](http://github.com/rvagg/through2). ## Usage ## [](https://nodei.co/npm/from2) ### `stream = from2([opts], read)` ### Where `opts` are the options to pass on to the `ReadableStream` constructor, and `read(size, next)` is called when data is requested from the stream. * `size` is the recommended amount of data (in bytes) to retrieve. * `next(err)` should be called when you're ready to emit more data. For example, here's a readable stream that emits the contents of a given string: ``` javascript var from = require('from2') function fromString(string) { return from(function(size, next) { // if there's no more content // left in the string, close the stream. if (string.length <= 0) return next(null, null) // Pull in a new chunk of text, // removing it from the string. var chunk = string.slice(0, size) string = string.slice(size) // Emit "chunk" from the stream. next(null, chunk) }) } // pipe "hello world" out // to stdout. fromString('hello world').pipe(process.stdout) ``` ### `stream = from2.obj([opts], read)` ### Shorthand for `from2({ objectMode: true }, read)`. ### `createStream = from2.ctor([opts], read)` ### If you're creating similar streams in quick succession you can improve performance by generating a stream **constructor** that you can reuse instead of creating one-off streams on each call. Takes the same options as `from2`, instead returning a constructor which you can use to create new streams. ### See Also - [from2-array](https://github.com/binocarlos/from2-array) - Create a from2 stream based on an array of source values. - [from2-string](https://github.com/yoshuawuyts/from2-string) - Create a stream from a string. Sugary wrapper around from2. ## License ## MIT. See [LICENSE.md](http://github.com/hughsk/from2/blob/master/LICENSE.md) for details.