send-http

A straightforward way to send data for http.ServerResponse.

It's like res.send, but:

• It accepts any kind of value (number, string, object, stream, etc).
• It leaves a response that already answered alone, rather than throwing at you.
• It determines Content-Type from the data: the type for values, the first bytes for streams.
• It optionally sets the status code as second argument.
• It tears down both ends when a stream fails or the client disconnects.
• It proxies an HTTP response with proxy, keeping the upstream status and the headers that describe the body.
• It's small (~110 LOC, one dependency).

Install

$ npm install send-http --save

It requires Node.js >= 24.

Usage

const send = require('send-http')
const http = require('http')
const got = require('got')

http.createServer((req, res) => {
  /* send with no body */
  send(res, 200)

  /* send a string */
  send(res, 200, 'foo')

  /* send an object */
  send(res, 200, { foo: 'bar' })

  /* send a number */
  send(res, 200, 1234)

  /* send a buffer */
  send(res, 200, Buffer.from('hello world'))

  /* send a stream  */
  send(res, 200, got.stream('https.//example.com'))
})

When the body is a stream, the Content-Type is detected from its first bytes via @kikobeats/set-content-type. An already set Content-Type is respected, and an unrecognized payload leaves it unset. proxy is different: when upstream sends Content-Type and it crosses the allowlist, that value is forwarded and the body is not sampled.

When a stream fails before anything reached the client, the response is closed without the error: an upstream that never answered is not a failure of the response itself. Once bytes are on the wire they cannot be retracted, so the response is destroyed with the failure and the client sees a reset rather than a truncated body that looks complete.

Use sendStream to decide what the client gets instead:

const { sendStream } = require('send-http')

http.createServer((req, res) => {
  sendStream(res, 200, got.stream('https://example.com'), {
    onError: (error, res) => {
      res.statusCode = error.code === 'ETIMEDOUT' ? 504 : 502
      res.end()
    }
  })
})

onError runs on the stream, before the response is torn down, so it can still write a reply. Write one and the response is left alone; write nothing and it is closed for you. Once the headers are out there is nothing left to answer with: send returns the response untouched rather than throwing ERR_HTTP_HEADERS_SENT at you from inside a listener, and the client sees the failure as a reset.

send takes the same options as a fourth argument and forwards them when the body is a stream, so send(res, 200, stream, { onError }) is sendStream(res, 200, stream, { onError }).

proxy

Relaying an HTTP response is not the same as sending a stream: status and body-descriptor headers come from the upstream once it answers.

const { proxy } = require('send-http')

http.createServer((req, res) => {
  proxy(res, got.stream('https://example.com/video.mp4'), {
    onError: (error, res) => send(res, 502, { error: error.message })
  })
})

onError follows the same rules as sendStream above.

headers is an allowlist of lowercase names that may cross; nothing else does. It defaults to STREAM_ALLOWED_HEADERS:

const { STREAM_ALLOWED_HEADERS } = require('send-http')

proxy(res, upstream, { headers: [...STREAM_ALLOWED_HEADERS, 'etag'] })

content-length is not in the default list: upstreams often declare a wrong length while still sending the full body, so the proxied response uses chunked transfer instead. Re-adding it takes that back, and a length the upstream got wrong truncates the response.

proxy accepts either a stream that emits response later, or an IncomingMessage that already answered:

proxy(res, got.stream(url))
http.get(url, upstream => proxy(res, upstream))

got.stream decompresses by default. Decoding hands over a different representation of the body, so content-encoding, content-length, content-range and etag from that hop are dropped rather than mislabel the bytes being piped. That holds however they got on the list, the default one or a custom one. Pass { decoded: false } to relay the compressed representation instead (same as piping an IncomingMessage), and all four cross with the bytes they describe.

When content-type crosses, the first byte reaches the client as soon as the upstream produces it. If it does not cross, Content-Type is sniffed from the first bytes like sendStream.

Teardown matches streams (see above): the upstream is destroyed when the client leaves, including before the upstream has answered.

create

Customizes the write of a buffered body (streams go through sendStream, and an empty body ends the response without a write to customize). The hook runs after the Content-Type and Content-Length are set, and receives the body as a Buffer whatever it was given:

const send = require('send-http').create((res, data) => {
  if (data.length > 6291456) {
    throw new Error('Payload size is over 6mb')
  }
  return res.end(data)
})

isStream

The predicate behind the dispatch, exported for reusing the same rule:

const { isStream } = require('send-http')

isStream(got.stream('https://example.com')) // => true
isStream({}) // => false

canAnswer

The guard behind the no-op: false once the headers went out or the response ended, which is when writing to it would throw. Use it to skip work whose only purpose was the answer:

const { canAnswer } = require('send-http')

if (canAnswer(res)) send(res, 500, { error: 'upstream failed' })

send already checks it, so an unconditional call is safe too: it returns the response untouched rather than throwing.

License

send-http © Kiko Beats, released under the MIT License. Authored and maintained by Kiko Beats with help from contributors.

kikobeats.com · GitHub Kiko Beats · X @Kikobeats