| var MapCache = require('./_MapCache'); |
| |
| /** Error message constants. */ |
| 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 `clear`, `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 != null && 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) || cache; |
| return result; |
| }; |
| memoized.cache = new (memoize.Cache || MapCache); |
| return memoized; |
| } |
| |
| // Expose `MapCache`. |
| memoize.Cache = MapCache; |
| |
| module.exports = memoize; |