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					74 lines
				
				2.2 KiB
			
		
		
			
		
	
	
					74 lines
				
				2.2 KiB
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											3 years ago
										 
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								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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