Writes working code, that has been tested for correctness, in the time allocated, following accepted best practices, in a way that can be easily maintained and enhanced, in collaboration with their team, and continuously improves their knowledge and skills throughout their career.
One of the APIs that gained a lot from the Firefox OS experiment was the service worker. Much like the web worker, it represents an isolated JS execution environment that is executed and stopped from the underlying platform. The only way to communicate with it is via message passing. The service worker provided a vast set of possibilities that were partially missing from web apps (as compared to mobile apps) and allowed more flexibility for handling caching in offline scenarios.