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JavaScript Async Iteration — exercises and bug fixes

5 hands-on exercises and 5 find-the-bug challenges for the JavaScript Async Iteration lesson. Every one is checked automatically in the browser — write the code, run it, and the tests tell you what still fails.

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Exercises(5)

  1. 1

    Consume an async generator

    easy10 min

    Use for await to collect values from an async generator.

  2. 2

    Transform each awaited value

    easy10 min

    Uppercase each item as it is awaited and yielded.

  3. 3

    Catch an error mid-stream

    easy10 min

    Catch a rejection that happens partway through an async generator.

  4. 4

    Mix plain and awaited yields

    easy10 min

    Yield some values immediately and one through a promise.

  5. 5

    Use for await on a plain generator

    medium10 min

    Show that for await also works on a synchronous generator.

Find the bug(5)

  1. 1

    Fix for of used on an async generator

    easy8 min

    An async generator needs for await, not a plain for of.

  2. 2

    Fix the missing async on the generator

    easy8 min

    await is only a keyword inside an async function, so using it in a plain generator will not even parse.

  3. 3

    Fix the rejection never caught

    easy8 min

    Without a try block, the loop's error escapes unhandled.

  4. 4

    Fix for await used outside an async function

    easy8 min

    for await can only be used inside an async function.

  5. 5

    Fix the values pushed before awaiting

    easy8 min

    The value should be pushed after it resolves, not the raw promise.

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