var MapCache = require('./_MapCache'); /** Used as the `TypeError` message for "Functions" methods. */ var FUNC_ERROR_TEXT = 'Expected a function'; /** * 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` * is invoked with the `this` binding of the memoized function. * * **Note:** The cache is exposed as the `cache` property on the memoized * function. Its creation may be customized by replacing the `_.memoize.Cache` * constructor with one whose instances implement the * [`Map`](http://ecma-international.org/ecma-262/7.0/#sec-properties-of-the-map-prototype-object) * method interface of `delete`, `get`, `has`, and `set`. * * @static * @memberOf _ * @since 0.1.0 * @category Function * @param {Function} func The function to have its output memoized. * @param {Function} [resolver] The function to resolve the cache key. * @returns {Function} Returns the new memoized function. * @example * * var object = { 'a': 1, 'b': 2 }; * var other = { 'c': 3, 'd': 4 }; * * var values = _.memoize(_.values); * values(object); * // => [1, 2] * * values(other); * // => [3, 4] * * object.a = 2; * values(object); * // => [1, 2] * * // Modify the result cache. * values.cache.set(object, ['a', 'b']); * values(object); * // => ['a', 'b'] * * // Replace `_.memoize.Cache`. * _.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; module.exports = memoize;