Move internal modules to “internal” folder.

.internal/cloneMap.js

@@ -0,0 +1,22 @@
+import addMapEntry from './.internal/addMapEntry.js';
+import arrayReduce from './.internal/arrayReduce.js';
+import mapToArray from './.internal/mapToArray.js';
+
+/** Used to compose bitmasks for cloning. */
+const CLONE_DEEP_FLAG = 1;
+
+/**
+ * Creates a clone of `map`.
+ *
+ * @private
+ * @param {Object} map The map to clone.
+ * @param {Function} cloneFunc The function to clone values.
+ * @param {boolean} [isDeep] Specify a deep clone.
+ * @returns {Object} Returns the cloned map.
+ */
+function cloneMap(map, isDeep, cloneFunc) {
+  const array = isDeep ? cloneFunc(mapToArray(map), CLONE_DEEP_FLAG) : mapToArray(map);
+  return arrayReduce(array, addMapEntry, new map.constructor);
+}
+
+export default cloneMap;