Hey everyone,
we've built an offline (highly experimental) version of our code editor on top of Service Workers and IndexedDB.
Basically, the service worker intercepts all requests for /preview//*, fetches files from the IndexedDB and passes them through a series of express.js middleware, everything inside the browser. Live code inspection is enabled via window + service messaging.
The most interesting concept in this project was to bring some server-side logic into the browser, specifically into the service worker, e.g. running css-autoprefixer through all CSS code before serving it.
Works on Chrome and FF.