Events as a stream in RxJS
RxJS interview exercise on Creating observables, difficulty 2 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 countClicks(target): for every "click" event on the target, emit how many clicks there have been so far (1, 2, 3 …). Listening starts with the subscription and ends with it.
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.