So siehts ganz gut aus !

node_modules/es5-ext/object/map-keys.js

@@ -0,0 +1,18 @@
+"use strict";
+
+var callable = require("./valid-callable")
+  , forEach  = require("./for-each")
+  , call     = Function.prototype.call;
+
+module.exports = function (obj, cb /*, thisArg*/) {
+	var result = {}, thisArg = arguments[2];
+	callable(cb);
+	forEach(
+		obj,
+		function (value, key, targetObj, index) {
+			result[call.call(cb, thisArg, key, value, this, index)] = value;
+		},
+		obj
+	);
+	return result;
+};