The browsers are getting better at optimizing memory use for small closures all the time, but there's still a long way to go. Here's a screenshot of the Chrome heap profiler for both cases:
I have one question. How to handle private methods in prototype/module pattern? If I declare private function in obj function declaration I can not access it in public functions attached to the prototype of obj. This is also true for module pattern. This problem arises when I need to add extra method later. How to overcome this situation?