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Higher Order Function withMemo

This library is result of this article: english, русский

withMemo is a dependency-free JavaScript library for memoizing functions. It is designed to improve the performance of expensive function calls by caching and reusing results for repeated calls with the same arguments. It supports various configuration options, such as custom cache keys, time-to-live (TTL) settings, and cache replacement policies.


$ npm install @eabgaryan/with-memo
# or with yarn
$ yarn add @eabgaryan/with-memo
# or with pnpm
$ pnpm add @eabgaryan/with-memo
Option Default value Description
getKey (arg) => arg A custom function for generating cache keys. Specifies how the arguments will be compared with each other. Will be called for each argument separately
getContextKey undefined Same as getKey but for context. If doesn't provided then context ignored.
getCacheStore () => new Map() The function should return an object with the same interface as Map. That structure will store the cache in tree form.
cacheRejectedPromise false If false then rejected promises will not be cached.
ttl undefined Time to live (in milliseconds) for the cache entries. If not specified, cache entries will not expire.
transformArgs (args) => args A function to transform the input arguments before they are passed to getKey function
cacheReplacementPolicy undefined An object with the following properties: maxSize (Number, required): The maximum number of cache entries. strategy (Function, required): The cache replacement strategy function. It takes an array of all cache entries and returns an array of cache entries to evict


Basic Usage

const expensiveOperation = (a, b) => {
  // Some expensive computation here...
  return a * b;

const memoizedExpensiveOperation = withMemo(expensiveOperation);

console.log(memoizedExpensiveOperation(2, 3)); // 6
console.log(memoizedExpensiveOperation(2, 3)); // 6 (cached result)

Advanced Usage

Custom Cache Key Function

const expensiveOperation = ({x, y}) => {
  // Some expensive computation here...
  return Math.sqrt(x**2 + y**2)

const memoizedExpensiveOperation = withMemo(expensiveOperation, {
  getKey: JSON.stringify,

console.log(memoizedExpensiveOperation({x: 2, y: 3})); // 5
console.log(memoizedExpensiveOperation({x: 2, y: 3})); // 5 (cached result)

TTL (Time to Live) Example

const randomNumber = () => Math.random();

const memoizedRandomNumber = withMemo(randomNumber, { ttl: 1000 });

const firstCall = memoizedRandomNumber();

setTimeout(() => {
  console.log(memoizedRandomNumber()); // Same as firstCall (cached result)
}, 500);

setTimeout(() => {
  console.log(memoizedRandomNumber()); // Different number (cache expired)
}, 1500);



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