A Subject as an event bus in RxJS
RxJS interview exercise on Subjects & sharing, difficulty 1 of 3. Solve it in the editor beside a worked example, or cold in Interview mode with the example hidden; the tests run the moment you do.
Write EventBus: emit(type, payload) publishes an event; on(type) returns an observable of the payloads of that type only. Subscribers receive events published after they subscribed; every subscriber of a type gets each of its events.
Each exercise pairs a worked example with a twin problem to solve in a real editor; the tests run the moment you do. Interview mode hides the example: solve it from memory, without the hint or the solution, and it counts as solved cold. Progress is saved in your browser, and in your account if you sign in.