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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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/** | 
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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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 | 
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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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 | 
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module.exports = memoize;
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