Alexandro.Net

Version 1.0.0

@stackline/concat-stream

writable stream that concatenates strings or binary data and calls a callback with the result

Independent maintenance of concat-stream 2.0.0. Original authors and licenses are retained.

Installation

# Preserve existing imports with an npm alias
npm install concat-stream@npm:@stackline/concat-stream@1.0.0
# Or use the scoped package name in your imports
npm install @stackline/concat-stream@1.0.0

Node.js: ['node >= 6.0']. Read the compatibility and maintenance notes before migrating.

Usage and API

The reference below may retain upstream package names. Use the alias installation above to run those imports with this Stackline release.

concat-stream

Writable stream that concatenates all the data from a stream and calls a callback with the result. Use this when you want to collect all the data from a stream into a single buffer.

Build Status

NPM

description

Streams emit many buffers. If you want to collect all of the buffers, and when the stream ends concatenate all of the buffers together and receive a single buffer then this is the module for you.

Only use this if you know you can fit all of the output of your stream into a single Buffer (e.g. in RAM).

There are also objectMode streams that emit things other than Buffers, and you can concatenate these too. See below for details.

Related

concat-stream is part of the mississippi stream utility collection which includes more useful stream modules similar to this one.

examples

Buffers

var fs = require('fs')
var concat = require('concat-stream')

var readStream = fs.createReadStream('cat.png')
var concatStream = concat(gotPicture)

readStream.on('error', handleError)
readStream.pipe(concatStream)

function gotPicture(imageBuffer) {
  // imageBuffer is all of `cat.png` as a node.js Buffer
}

function handleError(err) {
  // handle your error appropriately here, e.g.:
  console.error(err) // print the error to STDERR
  process.exit(1) // exit program with non-zero exit code
}

Arrays

var write = concat(function(data) {})
write.write([1,2,3])
write.write([4,5,6])
write.end()
// data will be [1,2,3,4,5,6] in the above callback

Uint8Arrays

var write = concat(function(data) {})
var a = new Uint8Array(3)
a[0] = 97; a[1] = 98; a[2] = 99
write.write(a)
write.write('!')
write.end(Buffer.from('!!1'))

See test/ for more examples

methods

var concat = require('concat-stream')

var writable = concat(opts={}, cb)

Return a writable stream that will fire cb(data) with all of the data that was written to the stream. Data can be written to writable as strings, Buffers, arrays of byte integers, and Uint8Arrays.

By default concat-stream will give you back the same data type as the type of the first buffer written to the stream. Use opts.encoding to set what format data should be returned as, e.g. if you if you don't want to rely on the built-in type checking or for some other reason.

If you don't specify an encoding, and the types can't be inferred (e.g. you write things that aren't in the list above), it will try to convert concat them into a Buffer.

If nothing is written to writable then data will be an empty array [].

error handling

concat-stream does not handle errors for you, so you must handle errors on whatever streams you pipe into concat-stream. This is a general rule when programming with node.js streams: always handle errors on each and every stream. Since concat-stream is not itself a stream it does not emit errors.

We recommend using end-of-stream or pump for writing error tolerant stream code.

license

MIT LICENSE

Upstream issues and maintenance review

Upstream origin and triage

Reviewed issues

Primary-source snapshot: 2026-09-29T00:21:59.613145+00:00. Most recently updated 100 open and 30 closed issue/PR entries; PRs removed. This is triage evidence, not a claim of exhaustive review.

Maintenance adoption with preserved runtime payload. No runtime defect correction is claimed. Reports remain visible for subsequent targeted reproduction.

The structured snapshot in .stackline/issue-triage.json also records recently closed reports. Issues for unrelated packages in shared monorepositories were qualified as outside this fork’s runtime scope. No maintainer was contacted.

Release files and references

Package bytes, npm provenance and the immutable GitHub release were verified for this version. Security checks describe the reviewed release; documented compatibility risks and upstream reports are not blanket claims of resolution.