Yes, `YUI_config`, and `YUI_config.conditions` are guaranteed by `express-yui` default configuration and the corresponding `req.app.expose(yui_config, 'window.YUI_config', {cache: true});` call.

`cs` is very clear, jajajaja: `c`ondition`s`, don't you get it? lol, this code is serialized and exposed without minification, trying to keep it smaller.