Iterate over promises, promise-returning or async/await functions in series or parallel. Support settle (fail-fast), concurrency (limiting) and hooks system (start, beforeEach, afterEach, finish)
- Install
- Usage
- Background
- API
- Options
- Hooks
- Item
- Finish hook
- Related
- Contributing
- Building docs
- Running tests
- Author
- Logo
- License
(TOC generated by verb using markdown-toc)
Install with npm
$ npm install each-promise --save
or install using yarn
$ yarn add each-promise
For more use-cases see the tests
const eachPromise = require('each-promise')
const arr = [
123,
'foo',
() => 456,
Promise.resolve(567)
false,
() => Promise.resolve(11)
]
eachPromise
.serial(arr)
.then((res) => {
console.log(res) // => [123, 'foo', 456, 567, false, 11]
})You may think why this exists, what is this for, why not Sindre's microlibs like p-map, p-map-series, p-settle, p-each-series or p-reduce.
They do their jobs okey, but in some cases they don't. And that's the my case. I need control over "fast fail" behavior, also known as "settle" or "bail". I need serial and parallel iteration, but parallel with concurrency too. They requires node v4, and uses native Promise constructor. I believe in that we should not use modern things if we don't need them, it is just syntax sugar. This package is written in way that works in node versions below v4 and also you can pass custom Promise constructor through options.Promise if you want.
- node@4 required
- no hooks system
- no settle / fail-fast / bail
- no custom Promise
- no real and meaningful tests
- concurrency control
Why not separate .serial and .parallel into own libs like Sindre did? Because the main core logic and difference is absolutely in just 2-3 lines of code and one if check. The main thing is that parallel uses for loop with concurrency combination, and series does not use loops, but recursive function calls.
For free you get hooks system. And really it cost nothing. It just able to be done, because the structure of the code and because I need such thing.
- node v0.10 and above
- custom Promise constructor
- real settle / fail fast
- hook system, through options
- very stable and well tested with real tests
- concurrency control
Iterate over
iterablein series (serially) with optionalopts(see options section) and optionalmapperfunction (see item section).
Params
<iterable>{Array}: iterable object like array with any type of values[mapper]{Function}: function to apply to each item initerable, see item section[opts]{Object}: see options sectionreturns{Promise}: Always resolved or rejected promise
Example
var delay = require('delay')
var eachPromise = require('each-promise')
var arr = [
() => delay(500).then(() => 1),
() => delay(200).then(() => { throw Error('foo') }),
() => delay(10).then(() => 3),
() => delay(350).then(() => 4),
() => delay(150).then(() => 5)
]
eachPromise
.serial(arr)
.then((res) => {
console.log(res) // [1, Error: foo, 3, 4, 5]
})
// see what happens when parallel
eachPromise
.parallel(arr)
.then((res) => {
console.log(res) // => [3, 5, Error: foo, 4, 1]
})
// pass `settle: false` if you want
// to stop after first error
eachPromise
.serial(arr, { settle: false })
.catch((err) => console.log(err)) // => Error: fooIterate concurrently over
iterablein parallel (support limiting withopts.concurrency) with optionalopts(see options section) and optionalmapperfunction (see item section).
Params
<iterable>{Array}: iterable object like array with any type of values[mapper]{Function}: function to apply to each item initerable, see item section[opts]{Object}: see options sectionreturns{Promise}: Always resolved or rejected promise
Example
var eachPromise = require('each-promise')
var arr = [
function one () {
return delay(200).then(() => {
return 123
})
},
Promise.resolve('foobar'),
function two () {
return delay(1500).then(() => {
return 345
})
},
delay(10).then(() => 'zero'),
function three () {
return delay(400).then(() => {
coffffnsole.log(3) // eslint-disable-line no-undef
return 567
})
},
'abc',
function four () {
return delay(250).then(() => {
return 789
})
},
function five () {
return delay(100).then(() => {
sasasa // eslint-disable-line no-undef
return 444
})
},
function six () {
return delay(80).then(() => {
return 'last'
})
}
]
// does not stop after first error
// pass `settle: false` if you want
eachPromise
.parallel(arr)
.then((res) => {
console.log(res)
// => [
// 'foobar',
// 'abc',
// 'zero',
// 'last',
// ReferenceError: sasasa is not defined,
// 123,
// 789,
// ReferenceError: coffffnsole is not defined
// 345
// ]
})Iterate over
iterablein series or parallel (default), depending on defaultopts. Passopts.serial: trueif you want to iterate in series, passopts.serial: falseor does not pass anything for parallel.
Params
<iterable>{Array}: iterable object like array with any type of values[mapper]{Function}: function to apply to each item initerable, see item section[opts]{Object}: see options sectionreturns{Promise}: Always resolved or rejected promise
Example
var delay = require('delay')
var eachPromise = require('each-promise')
var arr = [
123,
function () {
return delay(500).then(() => 456)
},
Promise.resolve(678),
function () {
return 999
},
function () {
return delay(200).then(() => 'foo')
}
]
eachPromise
.each(arr)
.then(function (res) {
console.log('done', res) // => [123, 678, 999, 'foo', 456]
})You have control over everything, through options.
Promise{Function}: custom Promise constructor to be used, defaults to nativemapper{Function}: function to apply to each item initerable, see item sectionsettle{Boolean}: iffalsestops after first error (also known as "fail-fast" or "bail"), defaulttrueflat{Boolean}: result array to contain only values, defaulttrueconcurrency{Number}: works only with.parallelmethod, defaults toiterablelengthstart{Function}: on start hook, see hooks sectionbeforeEach{Function}: called before each item initerable, see hooks sectionafterEach{Function}: called after each item initerable, see hooks sectionfinish{Function}: called at the end of iteration, see hooks sectioncontext{Object}: custom context to be passed to eachfniniterableargs{Array}: custom argument(s) to be pass tofn, given value is arrayified
You can do what you want between stages through hooks - start, before each, after each, finish.
start{Function}: called at the start of iteration, before anythingbeforeEach{Function}: passed withitem, index, arrargumentsitemis an object withvalue,reasonandindexproperties, see item sectionindexis the same asitem.indexarris the iterable object - array or object
afterEach{Function}: passed withitem, index, arrargumentsitemis an object withvalue,reasonandindexproperties, see item sectionindexis the same asitem.indexarris the iterable object - array or object
finish{Function}: called at the end of iteration, see finish hook section
That object is special object, that is passed to
beforeEachandafterEachhooks, also can be found inresultobject if you passopts.flat: falseoption. And passed toopts.mapperfunction too.
item.valueresolved/rejected promise value, if atbeforeEachhook it can befunctionitem.reasonmay not exist ifitem.value, if exist it is standard Error objectitem.indexis number, order of "executing", not the order that is defined initerable
This hooks is called when everything is finished / completed. At the very end of iteration. It is passed with
err, resultarguments where:
erris an Error object, ifopts.settle: false, otherwisenullresultis always an array with values or item objects ifopts.flat: false
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Pull requests and stars are always welcome. For bugs and feature requests, please create an issue.
Please read the contributing guidelines for advice on opening issues, pull requests, and coding standards.
If you need some help and can spent some cash, feel free to contact me at CodeMentor.io too.
In short: If you want to contribute to that project, please follow these things
- Please DO NOT edit README.md, CHANGELOG.md and .verb.md files. See "Building docs" section.
- Ensure anything is okey by installing the dependencies and run the tests. See "Running tests" section.
- Always use
npm run committo commit changes instead ofgit commit, because it is interactive and user-friendly. It uses commitizen behind the scenes, which follows Conventional Changelog idealogy. - Do NOT bump the version in package.json. For that we use
npm run release, which is standard-version and follows Conventional Changelog idealogy.
Thanks a lot! :)
Documentation and that readme is generated using verb-generate-readme, which is a verb generator, so you need to install both of them and then run verb command like that
$ npm install verbose/verb#dev verb-generate-readme --global && verb
Please don't edit the README directly. Any changes to the readme must be made in .verb.md.
Clone repository and run the following in that cloned directory
$ npm install && npm test
Charlike Mike Reagent
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Copyright © 2016-2018, Charlike Mike Reagent. Released under the MIT License.
This file was generated by verb-generate-readme, v0.4.3, on March 19, 2017.
Project scaffolded using charlike cli.
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