| var MapCache = require('../internal/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 coerced to a string and used as the |
| * 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-262/6.0/#sec-properties-of-the-map-prototype-object) |
| * method interface of `get`, `has`, and `set`. |
| * |
| * @static |
| * @memberOf _ |
| * @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 memoizing function. |
| * @example |
| * |
| * var upperCase = _.memoize(function(string) { |
| * return string.toUpperCase(); |
| * }); |
| * |
| * upperCase('fred'); |
| * // => 'FRED' |
| * |
| * // modifying the result cache |
| * upperCase.cache.set('fred', 'BARNEY'); |
| * upperCase('fred'); |
| * // => 'BARNEY' |
| * |
| * // replacing `_.memoize.Cache` |
| * var object = { 'user': 'fred' }; |
| * var other = { 'user': 'barney' }; |
| * var identity = _.memoize(_.identity); |
| * |
| * identity(object); |
| * // => { 'user': 'fred' } |
| * identity(other); |
| * // => { 'user': 'fred' } |
| * |
| * _.memoize.Cache = WeakMap; |
| * var identity = _.memoize(_.identity); |
| * |
| * identity(object); |
| * // => { 'user': 'fred' } |
| * identity(other); |
| * // => { 'user': 'barney' } |
| */ |
| 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; |
| return memoized; |
| } |
| |
| // Assign cache to `_.memoize`. |
| memoize.Cache = MapCache; |
| |
| module.exports = memoize; |