restream

restream

yarn add -E restream

Regular expression detection implemented as a transform Steam and regex-based buffer replacement stream to replace streamed data on-the-fly.

import restream, { replaceStream } from 'restream'

Table of Contents

• Table of Contents
• restream(regex: RegExp) => Transform
• replaceStream({re:RegExp, replacement:string }[]) => Transform
• replaceStream({re:RegExp, replacement: function(match, ...params) }[]) => Transform

restream(regex: RegExp) => Transform

Create a transform stream which will buffer incoming data and push regex results when matches can be made, i.e. when regex.exec returns non-null value. You will probably want to set the g flag on regexes most of the time.

/** yarn examples/restream.js **/
import restream from 'restream'
import { createReadable, createWritable } from './lib'

(async () => {
  try {
    const rs = createReadable('test-string-{12345}-{67890}')

    const stream = restream(/{(\d+)}/g) // create a transform stream
    rs.pipe(stream)

    const { data, ws } = createWritable()
    stream.pipe(ws)

    ws.once('finish', () => {
      console.log(data)
    })
  } catch (err) {
    console.error(err)
  }
})()

[ [ '{12345}',
    '12345',
    index: 12,
    input: 'test-string-{12345}-{67890}' ],
  [ '{67890}',
    '67890',
    index: 20,
    input: 'test-string-{12345}-{67890}' ] ]

replaceStream({re:RegExp, replacement:string }[]) => Transform

Creates a Transform stream which will make data available when an incoming chunk has been updated according to the regex input, which can be either a single regex object ({ re: /regex/, replacement: 'hello-world' }), or an array of such objects. A replacement can be either a string, or a function, which will be called by str.replace

/** yarn examples/replace-stream.js */
import Catchment from 'catchment'
import { replaceStream } from 'restream'
import { createReadable } from './lib'

(async () => {
  try {
    const stream = replaceStream([{
      re: /{{ user }}/,
      replacement: 'fred',
    }, {
      re: /{{ name }}/g,
      replacement: 'Fred',
    }, {
      re: /{{ stars }}/,
      replacement: '5',
    }])

    const rs = createReadable('Hello {{ name }}, your username is {{ user }} and you have {{ stars }} stars')
    rs.pipe(stream)
    const { promise } = new Catchment({
      rs: stream,
    })
    const res = await promise
    console.log(res)
  } catch (err) {
    console.error(err)
  }
})()

Output:

Hello Fred, your username is fred and you have 5 stars

replaceStream({re:RegExp, replacement: function(match, ...params) }[]) => Transform

You can replace matches using a function. See MDN for more documentation.

/** yarn examples/replace-function.js */
import { replaceStream } from '../src'
import Catchment from 'catchment'
import { createReadable } from './lib'

(async () => {
  try {
    const stream = replaceStream([{
      re: /__(\S+)__/g,
      replacement(match, p1) {
        return `<em>${p1}</em>`
      },
    }])
    const rs = createReadable('Hello __Fred__, your username is __fred__ and you have __5__ stars.')
    rs.pipe(stream)

    const { promise } = new Catchment({
      rs: stream,
    })
    const res = await promise

    console.log(res)
  } catch (err) {
    console.error(err)
  }
})()

Output:

Hello <em>Fred</em>, your username is <em>fred</em> and you have <em>5</em> stars

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(c) Art Deco Code 2018