Service worker?

I’ve spent an afternoon to understand what is service worker for bug 1145498, and I found it’s not only a worker, it’s also a proxy between client and server!

Some notes after reading this introduction:

• External events: “install”, “fetch”, “message”, and “activate”
  Fetch is the one which makes it a proxy, service worker will receive fetch events for everything on its registered location. Which it can leverage cache API to keep a local response.
• Works only for https
  Can only register for service workers on pages served over HTTPS since you don’t want any pieice of code can do strange things to your request.
• Can access IndexedDB API
• Possible overhead
  1. IPC
  2. Accessing cache
  3. Cloning request/response