Save an object — practice exercise

What you'll be asked to do

1. 1.Save an objectexercise · easy · 10 min

   Save a user object and read the name back.

   Passes when: #out should show Ada.

2. 2.Save an arrayexercise · easy · 10 min · practice plan

   Save a list of tags and count them after loading.

   Passes when: #out should show 3.

3. 3.Use a default when nothing is savedexercise · easy · 10 min · practice plan

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

   Passes when: #out should show empty.

4. 4.Update a stored objectexercise · easy · 10 min · practice plan

   Load, change a property, and save it again.

   Passes when: #out should show 2.

5. 5.Recover from bad dataexercise · medium · 10 min · practice plan

   Catch a parse failure and fall back to a default.

   Passes when: #out should show recovered.

6. 6.Fix the object saved directlybug fix · easy · 8 min

   Without stringify the object becomes useless text.

   Passes when: #out should show Ada.

7. 7.Fix the missing parsebug fix · easy · 8 min · practice plan

   The saved value is still a JSON string until parsed.

   Passes when: #out should show 3.

8. 8.Fix JSON.parse called on a missing keybug fix · easy · 8 min · practice plan

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

   Passes when: #out should show an object.

9. 9.Fix the update never saved backbug fix · easy · 8 min · practice plan

   Changing the loaded object does not save it automatically.

   Passes when: #out should show 2.

10. 10.Fix the unguarded parse of bad databug fix · easy · 8 min · practice plan

    Invalid JSON throws unless it is caught.

    Passes when: #out should show recovered.

Between them these tasks cover JSON.stringify, JSON.parse and Error handling.

Looking for a different chapter? See every practice set, or switch to the interview theory questions.