lightjs does not rely on a backend. It does not send the HTML/CSS/JS content to any external server (unless exported to jsfiddle.net).
lightjs does, however, rely on external libraries, if used. Various CDNs are used to load libraries like jQuery, Bootstrap and others.
lightjs is designed to be lightweight, not feature rich, while still providing some flexibility in development.
lightjs allows for direct conversion into a JS fiddle on jsfiddle.net (we are not affiliated).
lightjs is open source and available on GitHub: https://github.com/jorgenys/lightjs