from2
Convenience wrapper for ReadableStream, with an API lifted from "from" and "through2"
Last updated 4 years ago by mafintosh .
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from2 is a high-level module for creating readable streams that properly handle backpressure.

Convience wrapper for readable-stream's ReadableStream base class, with an API lifted from from and through2.

Usage

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:

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 - Create a from2 stream based on an array of source values.
  • from2-string - Create a stream from a string. Sugary wrapper around from2.

License

MIT. See LICENSE.md for details.

Current Tags

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