callback-sequence

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

Callbacks can be made async like gulp tasks.

Example

1var thunkify = require('callback-sequence')
2
3var Readable = require('stream').Readable
4var gulp = require('gulp')
5
6gulp.task('sequence', thunkify(
7  sync, async, promise, stream
8))
9
10gulp.task('parallel', thunkify(
11  [sync, async, promise, stream]
12))
13
14gulp.task('parallel-nested', thunkify(
15  // `async` and `promise` will be run in parallel
16  sync, [async, promise], stream
17))
18
19gulp.task('sequence-nested', thunkify(
20  // `async` and `promise` will be run in sequence
21  [sync, [async, promise], stream]
22))
23
24function sync() {
25}
26
27function async(cb) {
28  process.nextTick(cb)
29}
30
31function promise() {
32  return Promise.resolve()
33}
34
35function stream() {
36  var s = Readable()
37  s.push(null)
38  return s
39}
40

API

1var Runner = require('./lib/runner')
2var runner = new Runner({ input: false, output: false })
3
4exports = module.exports = runner.thunkify.bind(runner)
5exports.run = exports.sequence = runner.sequence.bind(runner)
6exports.parallel = runner.parallel.bind(runner)
7exports.series = runner.series.bind(runner)
8exports.Runner = Runner
9

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

1var Runner = require('callback-sequence').Runner
2
3var runner = Runner({ input: true })
4
5runner.thunkify(
6  function (a, b) {
7    // 3
8    return a + b
9  },
10  function (sum, next) {
11    process.nextTick(function () {
12      // 6
13      next(null, sum * 2)
14    })
15  },
16  function (product) {
17    return Promise.resolve().then(function () {
18      // 7
19      return product + 1
20    })
21  }
22)(1, 2)
23.then(function (res) {
24  // [7]
25  console.log(res)
26})
27
28

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.

1var runner = Runner()
2
3runner.thunkify(
4  function (res) {
5    return res + 1
6  },
7  function (res) {
8    return Promise.resolve()
9      .then(function () {
10        return res + 1
11      })
12  },
13  function (res, next) {
14    process.nextTick(function () {
15      next(null, res - 1, res + 1)
16    })
17  }
18)(1)
19.then(function (res) {
20  // [ 2, 4 ]
21  console.log(res)
22})
23

Runner.prototype.sequence(tasks)

Run tasks in sequence.

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

1var runner = Runner()
2
3runner.sequence([
4  function () { console.log(1) },
5  [
6    function (cb) {
7      setTimeout(function() {
8        console.log(3)
9        cb()
10      }, 0)
11    },
12    function () {
13      return new Promise(function (resolve) {
14        process.nextTick(function () {
15          console.log(2)
16          resolve()
17        })
18      })
19    },
20  ],
21  function () { console.log(4) },
22]).then(function () {
23  console.log('DONE')
24})
25
26// 1
27// 2
28// 3
29// 4
30// DONE
31

Callbacks can be added dynamically:

1var runner = Runner()
2
3var count = 5
4var tasks = []
5
6var res = []
7function task(next) {
8  process.nextTick(function () {
9    res.push(count)
10    if (--count > 0) {
11      tasks.push(task)
12    }
13    next()
14  })
15}
16runner.sequence(tasks).then(function () {
17  // [5, 4, 3, 2, 1]
18  console.log(res)
19})
20
21tasks.push(task)
22

Runner.prototype.parallel(tasks)

Run the specified tasks in parallel.

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

1var runner = Runner()
2
3var res = []
4runner.parallel([
5  function () { res.push(1) },
6  [
7    function () {
8      return Promise.resolve().then(function () {
9        res.push(4)
10      })
11    },
12    function () { res.push(5) },
13  ],
14  function (cb) {
15    setTimeout(function() {
16      res.push(3)
17      cb()
18    }, 0)
19  },
20  function (cb) {
21    res.push(2)
22    cb()
23  },
24])
25.then(function () {
26  // [1, 2, 4, 5, 3]
27  console.log(res)
28})
29

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.

1var runner = Runner()
2
3runner.series(
4  function () {
5    console.log(1)
6    return 1
7  },
8  [
9    function () {
10      return Promise.resolve().then(function () {
11        console.log(4)
12        return 4
13      })
14    },
15    function (cb) {
16      setTimeout(function() {
17        console.log(3)
18        cb(null, 3)
19      }, 0)
20    },
21    function () {
22      console.log(5)
23      return 5
24    },
25  ],
26  function (cb) {
27    console.log(2)
28    cb(null, 2)
29  }
30)
31.then(function (res) {
32  // 1
33  // 5
34  // 4
35  // 3
36  // 2
37  // [ [ 1  ], [ [ 4  ], [ 3  ], [ 5  ]  ], [ 2  ]  ]
38  console.log(res)
39})
40

Changelog