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https://github.com/feross/async-lru
A simple async LRU cache supporting O(1) set, get and eviction of old keys
https://github.com/feross/async-lru
async browser javascript lru lru-cache nodejs
Last synced: 14 days ago
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A simple async LRU cache supporting O(1) set, get and eviction of old keys
- Host: GitHub
- URL: https://github.com/feross/async-lru
- Owner: feross
- License: mit
- Created: 2017-02-17T02:39:12.000Z (almost 8 years ago)
- Default Branch: master
- Last Pushed: 2020-05-25T04:27:17.000Z (over 4 years ago)
- Last Synced: 2024-12-13T21:24:30.245Z (20 days ago)
- Topics: async, browser, javascript, lru, lru-cache, nodejs
- Language: JavaScript
- Homepage:
- Size: 19.5 KB
- Stars: 46
- Watchers: 3
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# async-lru [![travis][travis-image]][travis-url] [![npm][npm-image]][npm-url] [![downloads][downloads-image]][downloads-url] [![javascript style guide][standard-image]][standard-url]
[travis-image]: https://img.shields.io/travis/feross/async-lru/master.svg
[travis-url]: https://travis-ci.org/feross/async-lru
[npm-image]: https://img.shields.io/npm/v/async-lru.svg
[npm-url]: https://npmjs.org/package/async-lru
[downloads-image]: https://img.shields.io/npm/dm/async-lru.svg
[downloads-url]: https://npmjs.org/package/async-lru
[standard-image]: https://img.shields.io/badge/code_style-standard-brightgreen.svg
[standard-url]: https://standardjs.com
### A simple async LRU cache supporting O(1) set, get and eviction of old keys
Also works in the browser with [browserify](http://browserify.org/)!
## install
```
npm install async-lru
```
## usage
```js
const AsyncLRU = require('async-lru')
const fs = require('fs')
const lru = new AsyncLRU({
max: 2,
load: (key, cb) => {
fs.readFile(key, cb)
}
})
lru.get('file.txt', (err, value) => { // not in cache, calls load()
lru.get('file.txt', (err, value) => { // cached, will NOT call load()
// ...
})
})
```
### Differences from [`lru`](https://www.npmjs.com/package/lru)
Since values are fetched asynchronously, the `get` method takes a callback, rather
than returning the value synchronously.
While there is a `set(key, value)` method to manually seed the cache, typically
you'll just call `get` and let the `load` function fetch the key for you.
Keys must uniquely identify a single object, and must contain all the information
required to fetch an object.
## API
### `lru = AsyncLRU(opts)`
Create a new AsyncLRU cache. You must pass an options map with a `load` option:
```js
{
load: function (key, callback) {
callback(null, 'value') // get the data from an asyncronous store
}
}
```
Optional options:
```js
{
max: maxElementsToStore,
maxAge: maxAgeInMilliseconds
}
```
If you pass `max`, items will be evicted if the cache is storing more than `max` items.
If you pass `maxAge`, items will be evicted if they are older than `maxAge` when you access them.
**Returns**: the newly created AsyncLRU cache
### `lru.length`
The number of keys currently in the cache.
### `lru.keys`
Array of all the keys currently in the cache.
### `lru.set(key, value)`
Set the value of the key and mark the key as most recently used.
**Returns**: `value`
### `lru.get(key, [loadArgs], callback)`
Query the value of the key and mark the key as most recently used.
If the key is in the cache, then calls `callback(null, cached)` on `nextTick`.
Otherwise, calls `load(key, callback)` where `load` is the function that was
supplied in the options object. If it doesn't return an error, then cache the
result. Multiple `get` calls with the same `key` will only ever have a single
`load` call at the same time.
Optionally, specify `loadArgs` if you want a custom array of arguments to be passed
into `load` instead of `key`, like `load.apply(null, loadArgs.concat(callback))`.
### `lru.peek(key)`
Query the value of the key without marking the key as most recently used.
**Returns**: value of key if found; `undefined` otherwise.
### `lru.remove(key)`
Remove the value from the cache.
**Returns**: value of key if found; `undefined` otherwise.
### `lru.clear()`
Clear the cache. This method does **NOT** emit the `evict` event.
### `lru.on(event, callback)`
Respond to events. Currently only the `evict` event is implemented. When a key is
evicted, the callback is executed with an associative array containing the evicted
key: `{key: key, value: value}`.
## license
MIT. Copyright (c) [Feross Aboukhadijeh](http://feross.org).