Function memoize

src/helpers/set.js:778–799

* Creates a function that memoizes the result of `func`. If `resolver` is * provided, it determines the cache key for storing the result based on the * arguments provided to the memoized function. By default, the first argument * provided to the memoized function is used as the map cache key. The

(func, resolver)

 * _.memoize.Cache = WeakMap;
 */
function memoize(func, resolver) {
  if (
    typeof func != 'function' ||
    (resolver && typeof resolver != 'function')
  ) {
    throw new TypeError(FUNC_ERROR_TEXT);
  }
  var memoized = function () {
    var args = arguments,
      key = resolver ? resolver.apply(this, args) : args[0],
      cache = memoized.cache;

    if (cache.has(key)) {
      return cache.get(key);
    }
    var result = func.apply(this, args);
    memoized.cache = cache.set(key, result);
    return result;
  };
  memoized.cache = new (memoize.Cache || MapCache)();
  return memoized;
}

// Assign cache to `_.memoize`.
memoize.Cache = MapCache;