es-toolkit/docs/reference/function/memoize.md

memoize

Creates a memoized version of the provided function. The memoized function caches results based on the argument it receives, so if the same argument is passed again, it returns the cached result instead of recomputing it.

This works with functions that take zero or one argument. If your function takes multiple arguments, you should refactor it to accept a single object or array that combines those arguments.

If the argument is not primitive (e.g., arrays or objects), provide a getCacheKey function to generate a unique cache key for proper caching.

Signature

function memoize<F extends (...args: any) => any>(
  fn: F,
  options: {
    cache?: MemoizeCache<any, ReturnType<F>>;
    getCacheKey?: (args: Parameters<F>[0]) => unknown;
  } = {}
): F & { cache: MemoizeCache<any, ReturnType<F>> };

interface MemoizeCache<K, V> {
  set(key: K, value: V): void;
  get(key: K): V | undefined;
  has(key: K): boolean;
  delete(key: K): boolean | void;
  clear(): void;
  size: number;
}

Parameters

• fn (F) - The function to be memoized, which takes zero or just one argument.
• options: Optional configuration for the memoization.
  • options.cache (MemoizeCache<any, ReturnType<F>>): The cache object used to store results. Defaults to a new Map.
  • options.getCacheKey ((args: A) => unknown): An optional function to generate a unique cache key for each argument.

Returns

(F & { cache: MemoizeCache<any, ReturnType<F>> }): The memoized function with an additional cache property that exposes the internal cache.

Examples

import { memoize, MemoizeCache } from 'es-toolkit/function';

// Example using the default cache
const add = (x: number) => x + 10;
const memoizedAdd = memoize(add);

console.log(memoizedAdd(5)); // 15
console.log(memoizedAdd(5)); // 15 (cached result)
console.log(memoizedAdd.cache.size); // 1

// Example using a custom resolver
const sum = (arr: number[]) => arr.reduce((x, y) => x + y, 0);
const memoizedSum = memoize(sum, { getCacheKey: (arr: number[]) => arr.join(',') });
console.log(memoizedSum([1, 2])); // 3
console.log(memoizedSum([1, 2])); // 3 (cached result)
console.log(memoizedSum.cache.size); // 1

// Example using a custom cache implementation
class CustomCache<K, T> implements MemoizeCache<K, T> {
  private cache = new Map<K, T>();
  set(key: K, value: T): void {
    this.cache.set(key, value);
  }
  get(key: K): T | undefined {
    return this.cache.get(key);
  }
  has(key: K): boolean {
    return this.cache.has(key);
  }
  delete(key: K): boolean {
    return this.cache.delete(key);
  }
  clear(): void {
    this.cache.clear();
  }
  get size(): number {
    return this.cache.size;
  }
}
const customCache = new CustomCache<string, number>();
const memoizedSumWithCustomCache = memoize(sum, { cache: customCache });
console.log(memoizedSumWithCustomCache([1, 2])); // 3
console.log(memoizedSumWithCustomCache([1, 2])); // 3 (cached result)
console.log(memoizedAddWithCustomCache.cache.size); // 1