limit-concur

Features

- Tiny: only ~300 B minzipped
- Flexible: works for any function that returns a Promise

Install

``sh
$ npm i limit-concur
`

Usage

`js
import limitConcur from 'limit-concur'

const categories = await (
await fetch(https://api.chucknorris.io/jokes/categories)
).json()

let pendingRequests = 0
const getChuckNorrisJoke = async category => {
console.log(pending requests: ${++pendingRequests})
const response = await fetch(
https://api.chucknorris.io/jokes/random?category=${encodeURIComponent(category)},
)
const { value } = await response.json()
console.log(pending requests: ${--pendingRequests})
return value
}

const limitedGetChuckNorrisJoke = limitConcur(4, getChuckNorrisJoke)

// At most 4 requests are pending at any given time!
const jokes = await Promise.all(categories.map(limitedGetChuckNorrisJoke))
console.log(jokes)
//=> pending requests: 1
//=> pending requests: 2
//=> pending requests: 3
//=> pending requests: 4
//=> pending requests: 3
//=> pending requests: 4
//=> ...
//=> pending requests: 3
//=> pending requests: 2
//=> pending requests: 1
//=> pending requests: 0
//=> [
// 'Chuck Norris once rode a nine foot grizzly bear through an automatic car wash, instead of taking a shower.',
// "Chuck Norris is actually the front man for Apple. He let's Steve Jobs run the show when he's on a mission. Chuck Norris is always on a mission.",
// "Bill Gates thinks he's Chuck Norris. Chuck Norris actually laughed. Once.",
// 'Chuck Norris can install iTunes without installing Quicktime.',
// ...
// ]
`

$3

#### Replacing p-map

`js
import limitConcur from 'limit-concur'

const urls = [https://tomeraberba.ch, https://lfi.dev, https://npmjs.com]

const mapper = async url => {
const { redirected } = await fetch(url, { method: head })
return redirected
}

const results = await Promise.all(urls.map(limitConcur(2, mapper)))
console.log(results)
//=> [ false, false, true ]
`

#### Replacing p-all

`js
import limitConcur from 'limit-concur'

const actions = [
() => fetch(https://tomeraberba.ch),
() => fetch(https://lfi.dev),
() => checkSomething(),
() => doSomethingElse(),
]

const results = await Promise.all(
actions.map(limitConcur(2, action => action())),
)
console.log(results)
//=> [ ..., ..., ... ]
`

#### Replacing p-limit

`js
import limitConcur from 'limit-concur'

const limit = limitConcur(1, fn => fn())

const input = [
limit(() => fetchSomething(foo)),
limit(() => fetchSomething(bar)),
limit(() => doSomething()),
]

const results = await Promise.all(input)
console.log(results)
//=> [ ..., ..., ... ]
`

#### Replacing p-filter

`js
import limitConcur from 'limit-concur'

const urls = [https://tomeraberba.ch, https://lfi.dev, https://npmjs.com]

const filterer = async url => {
const { redirected } = await fetch(url, { method: head })
return !redirected
}

const results = await Promise.all(
urls.map(limitConcur(2, async url => ({ url, keep: await filterer(url) }))),
)
const filtered = results.flatMap(({ url, keep }) => (keep ? [url] : []))
console.log(filtered)
//=> [ 'https://tomeraberba.ch', 'https://lfi.dev' ]
`

#### Replacing p-props

`js
import limitConcur from 'limit-concur'

const urls = {
tomer: https://tomeraberba.ch,
lfi: https://lfi.dev,
npm: https://npmjs.com,
}

const mapper = async url => {
const { redirected } = await fetch(url, { method: head })
return redirected
}

const results = Object.fromEntries(
await Promise.all(
Object.entries(urls).map(
limitConcur(2, async ([name, url]) => [name, await mapper(url)]),
),
),
)
console.log(results)
//=> { tomer: false, lfi: false, npm: true }
``

Contributing

Stars are always welcome!

For bugs and feature requests,
please create an issue.

License

MIT ©
Tomer Aberbach \
Apache 2.0 ©
Google