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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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