# p-async-cache

> Cache the promise lookups and avoid fetching the same thing more than necessary

Latest version **1.0.3** (published 2017-11-27) · MIT license · 0 weekly downloads

## Install

```sh
npm install p-async-cache
pnpm add p-async-cache
yarn add p-async-cache
bun add p-async-cache
```

## Health

**Score 15/100 (F)** — status: abandoned.

Positive: no vulnerabilities.

Warnings: low downloads; no types; no esm support.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 1.0.3 |
| Published | 2017-11-27 |
| First published | 2017-03-07 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | none |
| Module format | CommonJS |
| Node | >=4 |
| Dependencies | 2 |
| Known vulnerabilities | 0 |
| Install scripts | no |
| Author | kaelzhang |
| Maintainers | kael |
| Keywords | p-async-cache, promise, async, cache, lru-cache |

## Links

- npm: https://www.npmjs.com/package/p-async-cache
- Repository: https://github.com/kaelzhang/p-async-cache
- Homepage: https://github.com/kaelzhang/p-async-cache#readme
- Issues: https://github.com/kaelzhang/p-async-cache/issues
- npm.io page: https://npm.io/package/p-async-cache

## Dependencies (2)

- [lru-cache](https://npm.io/package/lru-cache.md) ^4.0.2
- [pending-queue](https://npm.io/package/pending-queue.md) ^1.2.0

## Alternatives

- [memory-cache](https://npm.io/package/memory-cache.md) — 795.0K weekly downloads
- [@httptoolkit/proxy-agent](https://npm.io/package/@httptoolkit/proxy-agent.md) — 11.2K weekly downloads
- [express-cache-controller](https://npm.io/package/express-cache-controller.md) — 5.3K weekly downloads
- [http-cache-middleware](https://npm.io/package/http-cache-middleware.md) — 4.5K weekly downloads
- [cache2](https://npm.io/package/cache2.md) — 1.5K weekly downloads

## Recent versions

- 1.0.3 (latest) — 2017-11-27
- 1.0.2 — 2017-03-09
- 1.0.0 — 2017-03-09
- 0.0.0 — 2017-03-07

## README

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# p-async-cache

Cache the promise lookups and avoid fetching the same thing more than necessary.

## Install

```sh
$ npm install p-async-cache --save
```

## Usage

```js
import PAC from 'p-async-cache'

let counter = 0
const cache = new PAC({
  async load (userId) {
    counter ++
    return await getUserFromRemote(userId)
  }
})

function get () {
  cache.get(123).then(({value}) => {
    console.log(value, counter)
  })
}

get()
get()

// [object User] 1
// [object User] 1 (The counter still be 1)
```

## new AC(options)

- **options** `Object=`
  - stale `Boolean` whether allow stale value
  - stringify `function()=JSON.stringify` method to serialize the `params` to a cache key.
  - load `AsyncFunction(...params)|function(...params):Promise|function(...params)` accepts a normal synchronous function, a function that returns a promise, or an async function, and the `params` will be the parameters of the `.get(...params)` method.
  - other options that [lru-cache](https://www.npmjs.com/package/lru-cache) supports

### Example for `options.stale`

```js
import delay from 'delay'

const cache = new AC({
  stale: true,
  maxAge: 100,
  load (a, b) {
    return delay(1).then(() => a + b)
  }
})

cache.get(1, 2)
.then(({value, stale}) => {
  console.log(value)      // 3
  console.log(stale)      // false

  // Delay a timespan which is bigger than `maxAge`
  return delay(101).then(() => cache.get(1, 2))
})
.then(({value, stale}) => {
  console.log(value)      // 3
  console.log(stale)      // true (the value is stale)

  return delay(10).then(() => cache.get(1, 2))
})
.then(({value, stale}) => {
  console.log(value)      // 3
  console.log(stale)      // false (if the value is found as stale, it will refresh the value in the background)
})
```

## .get(...params)

- **params** `any` that will be passed into `options.load(...params)`

Returns `Promise`

Lookup the value in the cache,

- if found, then return.
- if not found,
  - if allow stale values, and the value is stale, then return the value, and refresh value in background.
  - otherwise, load the value with `load(...params)`

## Other methods of `lru-cache`

- `.reset()`
- `.has(...params)`
- `.peek(...params)`
- `.del(...params)`

## License

MIT

---
_Source: https://npm.io/package/p-async-cache · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._