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73 lines
2.2 KiB
73 lines
2.2 KiB
var MapCache = require('./_MapCache'); |
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/** Error message constants. */ |
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var FUNC_ERROR_TEXT = 'Expected a function'; |
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/** |
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* Creates a function that memoizes the result of `func`. If `resolver` is |
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* provided, it determines the cache key for storing the result based on the |
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* arguments provided to the memoized function. By default, the first argument |
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* provided to the memoized function is used as the map cache key. The `func` |
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* is invoked with the `this` binding of the memoized function. |
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* |
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* **Note:** The cache is exposed as the `cache` property on the memoized |
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* function. Its creation may be customized by replacing the `_.memoize.Cache` |
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* constructor with one whose instances implement the |
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* [`Map`](http://ecma-international.org/ecma-262/7.0/#sec-properties-of-the-map-prototype-object) |
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* method interface of `clear`, `delete`, `get`, `has`, and `set`. |
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* |
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* @static |
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* @memberOf _ |
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* @since 0.1.0 |
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* @category Function |
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* @param {Function} func The function to have its output memoized. |
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* @param {Function} [resolver] The function to resolve the cache key. |
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* @returns {Function} Returns the new memoized function. |
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* @example |
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* |
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* var object = { 'a': 1, 'b': 2 }; |
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* var other = { 'c': 3, 'd': 4 }; |
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* |
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* var values = _.memoize(_.values); |
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* values(object); |
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* // => [1, 2] |
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* |
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* values(other); |
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* // => [3, 4] |
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* |
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* object.a = 2; |
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* values(object); |
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* // => [1, 2] |
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* |
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* // Modify the result cache. |
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* values.cache.set(object, ['a', 'b']); |
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* values(object); |
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* // => ['a', 'b'] |
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* |
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* // Replace `_.memoize.Cache`. |
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* _.memoize.Cache = WeakMap; |
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*/ |
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function memoize(func, resolver) { |
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if (typeof func != 'function' || (resolver != null && typeof resolver != 'function')) { |
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throw new TypeError(FUNC_ERROR_TEXT); |
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} |
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var memoized = function() { |
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var args = arguments, |
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key = resolver ? resolver.apply(this, args) : args[0], |
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cache = memoized.cache; |
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if (cache.has(key)) { |
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return cache.get(key); |
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} |
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var result = func.apply(this, args); |
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memoized.cache = cache.set(key, result) || cache; |
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return result; |
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}; |
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memoized.cache = new (memoize.Cache || MapCache); |
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return memoized; |
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} |
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// Expose `MapCache`. |
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memoize.Cache = MapCache; |
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module.exports = memoize;
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