The async pipe in Angular

Angular interview exercise on RxJS interop, 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.

ChatComponent has a `messages observable built from the `incoming` Subject with scan, accumulating every message into…" /> observable built from the `incoming` Subject with scan, accumulating every message into…" /> observable built from the `incoming` Subject with scan, accumulating every message into…" /> observable built from the `incoming` Subject with scan, accumulating every message into…" /> observable built from the `incoming` Subject with scan, accumulating every message into…" /> observable built from the `incoming` Subject with scan, accumulating every message into…" /> observable built from the `incoming` Subject with scan, accumulating every message into…" /> observable built from the `incoming` Subject with scan, accumulating every message into an array (starting from []). Render them as <li> with the async pipe, and the count in <p class="count"> as "N messages".

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.

More RxJS interop in Angular

• An observable as a signal
• Debounced search with switchMap
• Subscriptions that end with the component
• A store driven by a Subject

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