Read a missing nested property — practice exercise

What you'll be asked to do

1. 1.Read a missing nested propertyexercise · easy · 10 min

   Use optional chaining to read a city that is not there, and show its type.

   Passes when: #out should show undefined.

2. 2.Read a nested property that existsexercise · easy · 10 min · practice plan

   Use optional chaining to read a city that is present.

   Passes when: #out should show London.

3. 3.Chain two levelsexercise · easy · 10 min · practice plan

   Use optional chaining twice on a path that stops halfway.

   Passes when: #out should show undefined.

4. 4.Use the bracket formexercise · easy · 10 min · practice plan

   Safely read the first item of an array that does not exist.

   Passes when: #out should show undefined.

5. 5.Keep a real zeroexercise · medium · 10 min · practice plan

   Show that optional chaining does not replace a value of zero.

   Passes when: #out should show 0.

6. 6.Fix the unsafe nested readbug fix · easy · 8 min

   The address is missing, so the path needs guarding.

   Passes when: #out should show no city.

7. 7.Fix the question mark in the wrong placebug fix · easy · 8 min · practice plan

   The guard is on the wrong step of the path.

   Passes when: #out should show London.

8. 8.Fix the missing bracket formbug fix · easy · 8 min · practice plan

   An index needs ?.[ ] rather than a plain dot.

   Passes when: #out should show safe.

9. 9.Fix the long guard chainbug fix · easy · 8 min · practice plan

   The nested checks work but are hard to read; use optional chaining.

   Passes when: #out should show Paris.

10. 10.Fix the zero treated as missingbug fix · easy · 8 min · practice plan

    Optional chaining only guards null and undefined, so a real zero must survive.

    Passes when: #out should show 0.

Between them these tasks cover Optional chaining, Nested data and Safe access.

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