# 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.
|