Memoizer

memoize.js

let set = (cache, val, k, ...rest) => {
  if (rest && rest.length) {
    if (!cache.has(k)) {
      cache.set(k, new Map());
    }
    set(cache.get(k), val, ...rest);
  } else {
    cache.set(k, val);
  }
};

let get = (cache, k, ...rest) => {
  if (cache.has(k)) {
    return rest && rest.length ? get(cache.get(k), ...rest) : cache.get(k);
  } else {
    return undefined;
  }
};

let memoizeHelper = (f) => {
  const cache = new Map();
  return (...args) => {
    let toRet = get(cache, ...args);
    if (!toRet) {
      toRet = f(...args);
      set(cache, toRet, ...args);
    }
    return toRet;
  };
};

let memoize = (memos) => {
  return Object.keys(memos).reduce((acc, k) => {
    acc[k] = memoizeHelper(memos[k]);
    return acc;
  }, {});
};


let memo = memoize({
  a: x => x*2,
  b: y => y^y, //Notice the bug here, should be `Math.pow(3, 3)`
  c: (x, y) => Math.pow(x,y),
  d: (x, y) => memo.b(x) + memo.b(y),
});

console.log(memo.a(2));
console.log(memo.b(3));
console.log(memo.c(4, 4));
console.log(memo.d(3, 2));