Function Cache and Async function timer

cache.js

function cacheFn(fn) {
  const cache = new Map(); // need .has, .get, .set methods.
  return (...args) => {
    const cacheKey = JSON.stringify(args.reduce((argsObject, arg, index) => { argsObject[index] = arg; return argsObject }, {}));
    if (cache.has(cacheKey)) {
      return cache.get(cacheKey);
    }
    const computed = fn(...args);
    cache.set(cacheKey, computed);
    return computed;
  };
}

function timeFnAsync(fn) {
  return async (...args) => {
    console.time("execution time");
    const promise = await fn(...args);
    console.timeEnd("execution time");
    return promise;
  };
}
/*
 * USAGE:
 *
 *  const api = {
 *    users: (limit, delay=2000) =>
 *      new Promise((resolve, reject) =>
 *        setTimeout(() => resolve([{id:1}, {id:2}, {id:3}, {id:4}, {id:5}].slice(0, limit)), delay)),
 *  };
 *
 *  api.users(3).then(results => console.log(results)) // logs Array with 3 Objects after 2 seconds
 *
 *  const cachedUsers = cacheFn(api.users)
 *
 *  cachedUsers(3).then(result => console.log(result)) // Cache miss : logs result after 2 seconds NOTE: this also populates the cache
 *
 *  cachedUsers(3).then(result => console.log(result)) // Cache hit : logs result immediately
 *
 *
*/