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- 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;
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