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https://github.com/sindresorhus/p-limit
Run multiple promise-returning & async functions with limited concurrency
https://github.com/sindresorhus/p-limit
Last synced: 1 day ago
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Run multiple promise-returning & async functions with limited concurrency
- Host: GitHub
- URL: https://github.com/sindresorhus/p-limit
- Owner: sindresorhus
- License: mit
- Created: 2016-10-21T07:51:54.000Z (about 8 years ago)
- Default Branch: main
- Last Pushed: 2024-12-19T15:46:45.000Z (26 days ago)
- Last Synced: 2025-01-06T22:02:00.183Z (8 days ago)
- Language: JavaScript
- Homepage:
- Size: 36.1 KB
- Stars: 2,110
- Watchers: 15
- Forks: 108
- Open Issues: 6
-
Metadata Files:
- Readme: readme.md
- License: license
- Security: .github/security.md
Awesome Lists containing this project
- awesome - sindresorhus/p-limit - Run multiple promise-returning & async functions with limited concurrency (JavaScript)
- awesome-web-cn - p-limit - 一个可以运行多个 promise-returning & async 函数并且限制并发数量的 JavaScript 库 (Uncategorized / Uncategorized)
- promise-fun - p-limit - returning & async functions with limited concurrency (Packages)
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- stars - p-limit - returning & async functions with limited concurrency | sindresorhus | 2076 | (JavaScript)
README
# p-limit
> Run multiple promise-returning & async functions with limited concurrency
*Works in Node.js and browsers.*
## Install
```sh
npm install p-limit
```
## Usage
```js
import pLimit from 'p-limit';
const limit = pLimit(1);
const input = [
limit(() => fetchSomething('foo')),
limit(() => fetchSomething('bar')),
limit(() => doSomething())
];
// Only one promise is run at once
const result = await Promise.all(input);
console.log(result);
```
## API
### pLimit(concurrency) default export
Returns a `limit` function.
#### concurrency
Type: `number`\
Minimum: `1`
Concurrency limit.
### limit(fn, ...args)
Returns the promise returned by calling `fn(...args)`.
#### fn
Type: `Function`
Promise-returning/async function.
#### args
Any arguments to pass through to `fn`.
Support for passing arguments on to the `fn` is provided in order to be able to avoid creating unnecessary closures. You probably don't need this optimization unless you're pushing a *lot* of functions.
### limit.activeCount
The number of promises that are currently running.
### limit.pendingCount
The number of promises that are waiting to run (i.e. their internal `fn` was not called yet).
### limit.clearQueue()
Discard pending promises that are waiting to run.
This might be useful if you want to teardown the queue at the end of your program's lifecycle or discard any function calls referencing an intermediary state of your app.
Note: This does not cancel promises that are already running.
### limit.concurrency
Get or set the concurrency limit.
### limitFunction(fn, options) named export
Returns a function with limited concurrency.
The returned function manages its own concurrent executions, allowing you to call it multiple times without exceeding the specified concurrency limit.
Ideal for scenarios where you need to control the number of simultaneous executions of a single function, rather than managing concurrency across multiple functions.
```js
import {limitFunction} from 'p-limit';
const limitedFunction = limitFunction(async () => {
return doSomething();
}, {concurrency: 1});
const input = Array.from({length: 10}, limitedFunction);
// Only one promise is run at once.
await Promise.all(input);
```
#### fn
Type: `Function`
Promise-returning/async function.
#### options
Type: `object`
#### concurrency
Type: `number`\
Minimum: `1`
Concurrency limit.
## FAQ
### How is this different from the [`p-queue`](https://github.com/sindresorhus/p-queue) package?
This package is only about limiting the number of concurrent executions, while `p-queue` is a fully featured queue implementation with lots of different options, introspection, and ability to pause the queue.
## Related
- [p-throttle](https://github.com/sindresorhus/p-throttle) - Throttle promise-returning & async functions
- [p-debounce](https://github.com/sindresorhus/p-debounce) - Debounce promise-returning & async functions
- [p-all](https://github.com/sindresorhus/p-all) - Run promise-returning & async functions concurrently with optional limited concurrency
- [More…](https://github.com/sindresorhus/promise-fun)