Memoize the last result, in async way.

async-memoize-one simply remembers the last arguments, and if the function is next called with the same arguments then it returns the previous result.

It's used for micro-caching scenarios, where you want to prevent perform an action previously done during a short period of time.

No need to worry about cache busting mechanisms such as maxAge, maxSize, exclusions and so on which can be prone to memory leaks.

Install

$ npm install async-memoize-one --save

Usage

const get = require('util').promisify(require('simple-get'))
const memoizeOne = require('async-memoize-one')

const fetchData = memoizeOne(url => get(`https://api.microlink.io?url=${url}`))

;(async () => {
  // fecthing data for first time
  console.time('fetch')
  await fetchData('https://example.com/one')
  console.timeEnd('fetch')

  // served data from cache; no fetching!
  console.time('fetch')
  await fetchData('https://example.com/one')
  console.timeEnd('fetch')

  // previous execution parameters are different, so fetching again
  console.time('fetch')
  await fetchData('https://example.com/two')
  console.timeEnd('fetch')

  // previous execution parameters are different, so fetching again
  console.time('fetch')
  await fetchData('https://example.com/one')
  console.timeEnd('fetch')
})()

API

memoizeOne(fn, [isEqual], [options])

fn

Required
Type: function

Promise-returning or async function to be memoized.

isEqual

Type: function
Default: fast-deep-equal

The compare function to determinate if both executions are the same.

An equality function should return true if the arguments are equal. If true is returned then the wrapped function will not be called.

options

cachePromiseRejection

Type: boolean
Default: false

Cache rejected promises.

License

async-memoize-one © microlink.io, released under the MIT License.
Authored and maintained by Kiko Beats with help from contributors.

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