74 lines
2.2 KiB
JavaScript
74 lines
2.2 KiB
JavaScript
![]() |
var MapCache = require('./_MapCache');
|
||
|
|
||
|
/** Used as the `TypeError` message for "Functions" methods. */
|
||
|
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 `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 && 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);
|
||
|
return result;
|
||
|
};
|
||
|
memoized.cache = new (memoize.Cache || MapCache);
|
||
|
return memoized;
|
||
|
}
|
||
|
|
||
|
// Assign cache to `_.memoize`.
|
||
|
memoize.Cache = MapCache;
|
||
|
|
||
|
module.exports = memoize;
|