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JavaScript async Error Handling — exercises and bug fixes

5 hands-on exercises and 5 find-the-bug challenges for the JavaScript async Error Handling 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

    Catch a rejected await

    easy10 min

    Await a rejected promise inside try and catch the error.

  2. 2

    Cover several awaits

    easy10 min

    Wrap two awaits in one try and catch the first failure.

  3. 3

    Clean up with finally

    easy10 min

    Catch the error then report that cleanup ran.

  4. 4

    Catch at the call site

    easy10 min

    Let the error escape and catch it where the function is called.

  5. 5

    Carry on after catching

    medium10 min

    Catch the failure and report a fallback value.

Find the bug(5)

  1. 1

    Fix the try that does not await

    easy8 min

    Without await the rejection escapes the try block.

  2. 2

    Fix the catch outside the async function

    easy8 min

    A plain try around the call cannot catch an async rejection.

  3. 3

    Fix the second step still running

    easy8 min

    After a failure the following awaits should be skipped.

  4. 4

    Fix the error swallowed silently

    easy8 min

    Catching without reporting hides the failure entirely.

  5. 5

    Fix finally used to handle the error

    easy8 min

    finally always runs but does not catch anything.

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