Pass a callback in — practice exercise

What you'll be asked to do

1. 1.Pass a callback inexercise · easy · 10 min

   Write a loader that hands its result to a callback.

   Passes when: #out should show got Ada.

2. 2.Use the error-first patternexercise · easy · 10 min · practice plan

   Call back with null for the error and a name for the value.

   Passes when: #out should show loaded Grace.

3. 3.Report a failureexercise · easy · 10 min · practice plan

   Call back with an error and report it.

   Passes when: #out should show error: not found.

4. 4.Nest two stepsexercise · easy · 10 min · practice plan

   Run one callback inside another and report both results.

   Passes when: #out should show one two.

5. 5.Use a named handlerexercise · medium · 10 min · practice plan

   Pass a named function as the callback rather than an inline one.

   Passes when: #out should show done Alan.

6. 6.Fix the result returned instead of passedbug fix · easy · 8 min

   Returning from inside a timer gives the caller nothing.

   Passes when: #out should show got Ada.

7. 7.Fix the arguments in the wrong orderbug fix · easy · 8 min · practice plan

   The error comes first and the value second.

   Passes when: #out should show loaded Grace.

8. 8.Fix the error never checkedbug fix · easy · 8 min · practice plan

   The failure is being reported as a success.

   Passes when: #out should show error: not found.

9. 9.Fix the callback called with bracketsbug fix · easy · 8 min · practice plan

   Passing callback() hands over its result, not the function.

   Passes when: #out should show got Ada.

10. 10.Fix the result used outside the callbackbug fix · easy · 8 min · practice plan

    The second half is added before the callback has supplied the first.

    Passes when: #out should show one two.

Between them these tasks cover Callbacks, Error-first pattern and Nesting.

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