LRU Memoize
npm install @digitalbazaar/lru-memoize
> A Memoized wrapper around the JavaScript lru-cache library.
- Background
- Install
- Usage
- Contribute
- License
lru-memoize is used to
to memoize promises
(as opposed to just the results of the operations),
which helps in high-concurrency use cases. (And in turn, it useslru-cache under the hood.)
To install locally (for development):
``
git clone https://github.com/digitalbazaar/lru-memoize.git
cd lru-memoize
npm install
To import:
`js`
import { LruCache } from '@digitalbazaar/lru-memoize';
// or
const { LruCache } = require('@digitalbazaar/lru-memoize');
The memoized LruCache constructor passes any options given to it through tolru-cache
the constructor, so see that repo for the full list of cache
management options. Commonly used ones include:
* max (default: 100) - maximum size of the cache.maxAge
* (default: 5 sec/5000 ms) - maximum age of an item in ms.updateAgeOnGet
* (default: false) - When using time-expiring entries withmaxAge
, setting this to true will make each entry's effective time update to
the current time whenever it is retrieved from cache, thereby extending the
expiration date of the entry.
This library is useful for caching (in a deterministic memoized fashion) expensive or long-running functions, such as
API requests, database lookups, and so on.
For example, say you have a function fetchStatus() that retrieves a result from a web API (here, simulated with adelay() wait). To cache the result of this function:
`js
import { LruCache } from '@digitalbazaar/lru-memoize';
// Cache expiration/TTL: 5 seconds
const myCache = new LruCache({ maxAge: 5000 });
async function fetchStatus() {
// simulate an async task
await delay(100);
executedTestFn = true;
return {success: true, timestamp: Date.now()};
}
// Load the cached result if it's present, otherwise, perform the operation
const result = await myCache.memoize({
key: 'myApiResults',
fn: fetchStatus
});
// You can also memoize a particular call to a function, using anonymous arrow functions:
const url = 'https://api.example';
const result = await myCache.memoize({
key: 'myResults',
fn: async () => fetchMyResultsFromWeb({ url })
});
`
The key param is used to namespace the caches, in case the same LruCache` instance is being used to cache different
types of operations/functions.
PRs accepted.
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