Bump to v4.0.0.

internal/MapCache.js

@@ -1,21 +1,28 @@
+import mapClear from './mapClear';
 import mapDelete from './mapDelete';
 import mapGet from './mapGet';
 import mapHas from './mapHas';
 import mapSet from './mapSet';
 
 /**
- * Creates a cache object to store key/value pairs.
+ * Creates a map cache object to store key-value pairs.
  *
  * @private
- * @static
- * @name Cache
- * @memberOf _.memoize
+ * @param {Array} [values] The values to cache.
  */
-function MapCache() {
-  this.__data__ = {};
+function MapCache(values) {
+  var index = -1,
+      length = values ? values.length : 0;
+
+  this.clear();
+  while (++index < length) {
+    var entry = values[index];
+    this.set(entry[0], entry[1]);
+  }
 }
 
-// Add functions to the `Map` cache.
+// Add functions to the `MapCache`.
+MapCache.prototype.clear = mapClear;
 MapCache.prototype['delete'] = mapDelete;
 MapCache.prototype.get = mapGet;
 MapCache.prototype.has = mapHas;