102 lines
2.7 KiB
Markdown
102 lines
2.7 KiB
Markdown
# p-limit
|
|
|
|
> Run multiple promise-returning & async functions with limited concurrency
|
|
|
|
## Install
|
|
|
|
```
|
|
$ npm install p-limit
|
|
```
|
|
|
|
## Usage
|
|
|
|
```js
|
|
const pLimit = require('p-limit');
|
|
|
|
const limit = pLimit(1);
|
|
|
|
const input = [
|
|
limit(() => fetchSomething('foo')),
|
|
limit(() => fetchSomething('bar')),
|
|
limit(() => doSomething())
|
|
];
|
|
|
|
(async () => {
|
|
// Only one promise is run at once
|
|
const result = await Promise.all(input);
|
|
console.log(result);
|
|
})();
|
|
```
|
|
|
|
## API
|
|
|
|
### pLimit(concurrency)
|
|
|
|
Returns a `limit` function.
|
|
|
|
#### concurrency
|
|
|
|
Type: `number`\
|
|
Minimum: `1`\
|
|
Default: `Infinity`
|
|
|
|
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.
|
|
|
|
## 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-queue](https://github.com/sindresorhus/p-queue) - Promise queue with concurrency control
|
|
- [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)
|
|
|
|
---
|
|
|
|
<div align="center">
|
|
<b>
|
|
<a href="https://tidelift.com/subscription/pkg/npm-p-limit?utm_source=npm-p-limit&utm_medium=referral&utm_campaign=readme">Get professional support for this package with a Tidelift subscription</a>
|
|
</b>
|
|
<br>
|
|
<sub>
|
|
Tidelift helps make open source sustainable for maintainers while giving companies<br>assurances about security, maintenance, and licensing for their dependencies.
|
|
</sub>
|
|
</div>
|