@jill64/lru-memoizer

Memoize functions results using an lru-cache.

Installation

npm i lru-memoizer --save

Intro

This module uses an lru-cache internally to cache the results of an async function.

The load function can have N parameters and the last one must be a callback. The callback should be an errback (first parameter is err).

The hash function purpose is generate a custom hash for storing results. It has all the arguments applied to it minus the callback, and must return a synchronous string.

The disable function allows you to conditionally disable the use of the cache. Useful for test environments.

The freeze option (defaults to false) allows you to deep-freeze the result of the async function.

The clone option (defaults to false) allows you to deep-clone the result every time is returned from the cache.

Usage

const memoizer = require('lru-memoizer');

const memoizedGet = memoizer({
  //defines how to load the resource when
  //it is not in the cache.
  load: function (options, callback) {
    request.get(options, callback);
  },

  //defines how to create a cache key from the params.
  hash: function (options) {
    return options.url + qs.stringify(options.qs);
  },

  //don't cache in test environment
  disable: isTestEnv(),

  //all other params for the LRU cache.
  max: 100,
  maxAge: 1000 * 60
});

memoizedGet({
  url: 'https://google.com',
  qs: { foo: 123 }
}, function (err, result, body) {
 //console.log(body);
})

Synchronous lru-memoizer

Use memoizer.sync to cache things that are slow to calculate, methods returning promises, or only if you don't want to use a callback and want it synchronous.

const memoizer = require('lru-memoizer');
const memoizedGet = memoizer.sync({
  //defines how to load the resource when
  //it is not in the cache.
  load: function (params) {
    return somethingHardToCompute();
  },

  //defines how to create a cache key from the params.
  hash: function (params) {
    return params.foo;
  },

  //all other params for the LRU cache.
  max: 100,
  maxAge: 1000 * 60
});

Similar modules

This module is very similar to async-cache^(deprecated), the main difference is the hash function.

License

MIT 2016 - José F. Romaniello