add hw2

node_modules/lodash-es/memoize.js

@@ -0,0 +1,73 @@
+import MapCache from './_MapCache.js';
+
+/** 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;
+
+export default memoize;