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JavaScript Storing Objects — exercises and bug fixes

5 hands-on exercises and 5 find-the-bug challenges for the JavaScript Storing Objects 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

    Save an object

    easy10 min

    Save a user object and read the name back.

  2. 2

    Save an array

    easy10 min

    Save a list of tags and count them after loading.

  3. 3

    Use a default when nothing is saved

    easy10 min

    Fall back to an empty object when the key is missing.

  4. 4

    Update a stored object

    easy10 min

    Load, change a property, and save it again.

  5. 5

    Recover from bad data

    medium10 min

    Catch a parse failure and fall back to a default.

Find the bug(5)

  1. 1

    Fix the object saved directly

    easy8 min

    Without stringify the object becomes useless text.

  2. 2

    Fix the missing parse

    easy8 min

    The saved value is still a JSON string until parsed.

  3. 3

    Fix JSON.parse called on a missing key

    easy8 min

    JSON.parse(null) quietly parses as the value null instead of an object.

  4. 4

    Fix the update never saved back

    easy8 min

    Changing the loaded object does not save it automatically.

  5. 5

    Fix the unguarded parse of bad data

    easy8 min

    Invalid JSON throws unless it is caught.

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