What is a lightweight JS framework for implementing a window interface?

Question

JavaScript

I need to write an admin panel for a website.
At first I decided to stop at ExtJS, but in principle such a "monster" will not be needed.
You need something similar, with the following requirements:
1. Implementation of the window interface, while not slowing down on 10+ windows.
2. Support for basic widgets: Input, Select, Button, Toolbar (optional), etc.
3. JSON and Ajax support.

Do not offer jQuery UI, as one of the projects had to abandon it in favor of ExtJS, but perhaps there is something else.

Answer 1

fstoke.me/jquery/window

Answer 2

Write yourself if you need something big.