Return a fallback — practice exercise

What you'll be asked to do

1. 1.Return a fallbackexercise · easy · 10 min

   Parse the text and return null when it fails.

   Passes when: #out should show nothing parsed.

2. 2.Fail fast on bad inputexercise · easy · 10 min · practice plan

   Check the types at the top and throw immediately.

   Passes when: #out should show must be numbers.

3. 3.Use a guard clauseexercise · easy · 10 min · practice plan

   Return a default rather than throwing for missing input.

   Passes when: #out should show Hello stranger.

4. 4.Add context when rethrowingexercise · easy · 10 min · practice plan

   Replace the parse error with a clearer message.

   Passes when: #out should show settings are not valid JSON.

5. 5.Handle at the boundaryexercise · medium · 10 min · practice plan

   Let the loop fail and catch once at the top.

   Passes when: #out should show stopped because step two failed.

6. 6.Fix the missing input checkbug fix · easy · 8 min

   With no check the text is coerced and a wrong answer is returned.

   Passes when: #out should show must be numbers.

7. 7.Fix the error caught and ignoredbug fix · easy · 8 min · practice plan

   Catching without acting hides a genuine bug.

   Passes when: #out should show TypeError.

8. 8.Fix the rethrow with no new informationbug fix · easy · 8 min · practice plan

   Rethrowing the same message adds nothing.

   Passes when: #out should show settings are not valid JSON.

9. 9.Fix the throw where a default would dobug fix · easy · 8 min · practice plan

   A missing name is expected, so return a greeting instead.

   Passes when: #out should show Hello stranger.

10. 10.Fix the handler inside the loopbug fix · easy · 8 min · practice plan

    One handler at the boundary is enough.

    Passes when: #out should show stopped because step two failed.

Between them these tasks cover Fail fast, Guard clauses and Rethrowing.

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