callback-sequence

Make a new callback to run callbacks in sequence or parallel.

Callbacks can be made async like gulp tasks.

Example

var thunkify = require('callback-sequence')

var Readable = require('stream').Readable
var gulp = require('gulp')

gulp.task('sequence', thunkify(
  sync, async, promise, stream
))

gulp.task('parallel', thunkify(
  [sync, async, promise, stream]
))

gulp.task('parallel-nested', thunkify(
  // `async` and `promise` will be run in parallel
  sync, [async, promise], stream
))

gulp.task('sequence-nested', thunkify(
  // `async` and `promise` will be run in sequence
  [sync, [async, promise], stream]
))

function sync() {
}

function async(cb) {
  process.nextTick(cb)
}

function promise() {
  return Promise.resolve()
}

function stream() {
  var s = Readable()
  s.push(null)
  return s
}

API

var Runner = require('./lib/runner')
var runner = new Runner({ input: false, output: false })

exports = module.exports = runner.thunkify.bind(runner)
exports.run = exports.sequence = runner.sequence.bind(runner)
exports.parallel = runner.parallel.bind(runner)
exports.series = runner.series.bind(runner)
exports.Runner = Runner

Runner

var runner = Runner(opts) Create a new runner instance.

opts

input

Specify whether to pass the results of the previous callback to the next as arguments.

Type: Boolean

Default: true

var Runner = require('callback-sequence').Runner

var runner = Runner({ input: true })

runner.thunkify(
  function (a, b) {
    // 3
    return a + b
  },
  function (sum, next) {
    process.nextTick(function () {
      // 6
      next(null, sum * 2)
    })
  },
  function (product) {
    return Promise.resolve().then(function () {
      // 7
      return product + 1
    })
  }
)(1, 2)
.then(function (res) {
  // [7]
  console.log(res)
})

output

Specify whether to deliver results.

Type: Boolean

Default: true

If false, the final results will always be [].

run

Specify a runner function to run each callback.

Type: Function, Object

Default: null

If Function, it receives a callback followed by a list of arguments, and should return a promise to fetch the results (Array).

If Object, it is passed to Runner of run-callback to create a runner function.

cb = Runner.prototype.thunkify(...tasks)

Return a callback to run the specified tasks in the appearance order.

var runner = Runner()

runner.thunkify(
  function (res) {
    return res + 1
  },
  function (res) {
    return Promise.resolve()
      .then(function () {
        return res + 1
      })
  },
  function (res, next) {
    process.nextTick(function () {
      next(null, res - 1, res + 1)
    })
  }
)(1)
.then(function (res) {
  // [ 2, 4 ]
  console.log(res)
})

Runner.prototype.sequence(tasks)

Run tasks in sequence.

NOTE: directly nested array of tasks will be run with Runner.prototype.parallel.

var runner = Runner()

runner.sequence([
  function () { console.log(1) },
  [
    function (cb) {
      setTimeout(function() {
        console.log(3)
        cb()
      }, 0)
    },
    function () {
      return new Promise(function (resolve) {
        process.nextTick(function () {
          console.log(2)
          resolve()
        })
      })
    },
  ],
  function () { console.log(4) },
]).then(function () {
  console.log('DONE')
})

// 1
// 2
// 3
// 4
// DONE

Callbacks can be added dynamically:

var runner = Runner()

var count = 5
var tasks = []

var res = []
function task(next) {
  process.nextTick(function () {
    res.push(count)
    if (--count > 0) {
      tasks.push(task)
    }
    next()
  })
}
runner.sequence(tasks).then(function () {
  // [5, 4, 3, 2, 1]
  console.log(res)
})

tasks.push(task)

Runner.prototype.parallel(tasks)

Run the specified tasks in parallel.

NOTE: directly nested array of tasks will be run with Runner.prototype.sequence.

var runner = Runner()

var res = []
runner.parallel([
  function () { res.push(1) },
  [
    function () {
      return Promise.resolve().then(function () {
        res.push(4)
      })
    },
    function () { res.push(5) },
  ],
  function (cb) {
    setTimeout(function() {
      res.push(3)
      cb()
    }, 0)
  },
  function (cb) {
    res.push(2)
    cb()
  },
])
.then(function () {
  // [1, 2, 4, 5, 3]
  console.log(res)
})

Runner.prototype.series(...tasks)

Run tasks in sequence.

However, while the results of sequence is that of the last task, the results of series is an array containing all results of the tasks.

In addition, the results of the previous task will not be passed to the next as arguments.

NOTE: each element will be passed to Runner.prototype.sequence.

var runner = Runner()

runner.series(
  function () {
    console.log(1)
    return 1
  },
  [
    function () {
      return Promise.resolve().then(function () {
        console.log(4)
        return 4
      })
    },
    function (cb) {
      setTimeout(function() {
        console.log(3)
        cb(null, 3)
      }, 0)
    },
    function () {
      console.log(5)
      return 5
    },
  ],
  function (cb) {
    console.log(2)
    cb(null, 2)
  }
)
.then(function (res) {
  // 1
  // 5
  // 4
  // 3
  // 2
  // [ [ 1  ], [ [ 4  ], [ 3  ], [ 5  ]  ], [ 2  ]  ]
  console.log(res)
})

Changelog