Projekt

Obecné

Profil

Stáhnout (2.17 KB) Statistiky
| Větev: | Revize:
1
var MapCache = require('./_MapCache');
2

    
3
/** Error message constants. */
4
var FUNC_ERROR_TEXT = 'Expected a function';
5

    
6
/**
7
 * Creates a function that memoizes the result of `func`. If `resolver` is
8
 * provided, it determines the cache key for storing the result based on the
9
 * arguments provided to the memoized function. By default, the first argument
10
 * provided to the memoized function is used as the map cache key. The `func`
11
 * is invoked with the `this` binding of the memoized function.
12
 *
13
 * **Note:** The cache is exposed as the `cache` property on the memoized
14
 * function. Its creation may be customized by replacing the `_.memoize.Cache`
15
 * constructor with one whose instances implement the
16
 * [`Map`](http://ecma-international.org/ecma-262/7.0/#sec-properties-of-the-map-prototype-object)
17
 * method interface of `clear`, `delete`, `get`, `has`, and `set`.
18
 *
19
 * @static
20
 * @memberOf _
21
 * @since 0.1.0
22
 * @category Function
23
 * @param {Function} func The function to have its output memoized.
24
 * @param {Function} [resolver] The function to resolve the cache key.
25
 * @returns {Function} Returns the new memoized function.
26
 * @example
27
 *
28
 * var object = { 'a': 1, 'b': 2 };
29
 * var other = { 'c': 3, 'd': 4 };
30
 *
31
 * var values = _.memoize(_.values);
32
 * values(object);
33
 * // => [1, 2]
34
 *
35
 * values(other);
36
 * // => [3, 4]
37
 *
38
 * object.a = 2;
39
 * values(object);
40
 * // => [1, 2]
41
 *
42
 * // Modify the result cache.
43
 * values.cache.set(object, ['a', 'b']);
44
 * values(object);
45
 * // => ['a', 'b']
46
 *
47
 * // Replace `_.memoize.Cache`.
48
 * _.memoize.Cache = WeakMap;
49
 */
50
function memoize(func, resolver) {
51
  if (typeof func != 'function' || (resolver != null && typeof resolver != 'function')) {
52
    throw new TypeError(FUNC_ERROR_TEXT);
53
  }
54
  var memoized = function() {
55
    var args = arguments,
56
        key = resolver ? resolver.apply(this, args) : args[0],
57
        cache = memoized.cache;
58

    
59
    if (cache.has(key)) {
60
      return cache.get(key);
61
    }
62
    var result = func.apply(this, args);
63
    memoized.cache = cache.set(key, result) || cache;
64
    return result;
65
  };
66
  memoized.cache = new (memoize.Cache || MapCache);
67
  return memoized;
68
}
69

    
70
// Expose `MapCache`.
71
memoize.Cache = MapCache;
72

    
73
module.exports = memoize;
(479-479/634)