Caching is fun ! A higher order function to add caching on your pure function.

withCache.js

/**
 * @typedef {Object} CacheResponse
 * @property {any} data - The value that you a general call would return.
 * @property {Object} cache - The cache store merged with the current function call.
 */

/**
 * Caching function or memoizer that uses a custom hashing key algo.

 * @param {function} fn - Pure function whose value you want to cache.
 * @param {Array} args - The list of arguments you want to call 'fn' with.
 * @param {Object} cache - Bunch of key value pairs that is literally your cache store.
 * @param {function} hashingFunction - The hashing algo appropriate for your case.

 * @return {CacheResponse} 
 */

const withCache = function (fn, args, cache, hashingFunction) {
  const cacheKey = hashingFunction(args);
  if(!cache[cacheKey]) {
    cache[cacheKey] = fn(...args);
  }
  return {data: cache[cacheKey], cache: cache};
}

/* Usage */

const add = (x,y) => x + y;
const hashFunction = args => JSON.stringify(args);
let cache = {}
const response = withCache(add, [1,2], cache, hashFunction);
cache = response["cache"];
const data = response["data"];