Bump to v4.0.0.

mapKeys.js

@@ -0,0 +1,32 @@
+import baseForOwn from './internal/baseForOwn';
+import baseIteratee from './internal/baseIteratee';
+
+/**
+ * The opposite of `_.mapValues`; this method creates an object with the
+ * same values as `object` and keys generated by running each own enumerable
+ * property of `object` through `iteratee`.
+ *
+ * @static
+ * @memberOf _
+ * @category Object
+ * @param {Object} object The object to iterate over.
+ * @param {Function|Object|string} [iteratee=_.identity] The function invoked per iteration.
+ * @returns {Object} Returns the new mapped object.
+ * @example
+ *
+ * _.mapKeys({ 'a': 1, 'b': 2 }, function(value, key) {
+ *   return key + value;
+ * });
+ * // => { 'a1': 1, 'b2': 2 }
+ */
+function mapKeys(object, iteratee) {
+  var result = {};
+  iteratee = baseIteratee(iteratee, 3);
+
+  baseForOwn(object, function(value, key, object) {
+    result[iteratee(value, key, object)] = value;
+  });
+  return result;
+}
+
+export default mapKeys;