Giving up on a slow source in RxJS
RxJS interview exercise on Timing, difficulty 3 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 withTimeout(source$, ms, fallback$): if the source's FIRST value takes longer than ms milliseconds, switch to fallback$ (its values, its completion). A source that is fast enough is passed through untouched, however long later values take.
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.