Pass a callback — practice exercise

What you'll be asked to do

1. 1.Pass a callbackexercise · easy · 10 min

   Pass a function to another function and show what it returns.

   Passes when: #out should show done.

2. 2.A named callbackexercise · easy · 10 min · practice plan

   Pass a named function to map to double each value, then join with commas.

   Passes when: #out should show 2,4,6.

3. 3.A callback with an argumentexercise · easy · 10 min · practice plan

   Call the callback three times with the count, collecting the values.

   Passes when: #out should show 1-2-3.

4. 4.Filter with a callbackexercise · easy · 10 min · practice plan

   Use filter with a callback to keep numbers above 4, then join with commas.

   Passes when: #out should show 8,12.

5. 5.Transform with a callbackexercise · medium · 10 min · practice plan

   Write a process function that applies a callback to every item. Square them and join with commas.

   Passes when: #out should show 1,4,9,16.

6. 6.Fix the callback called too earlybug fix · easy · 8 min

   The brackets run the function and pass its result instead.

   Passes when: #out should show done.

7. 7.Fix the wrong operationbug fix · easy · 8 min · practice plan

   The callback adds 2 instead of doubling.

   Passes when: #out should show 2,4,6.

8. 8.Fix the ignored argumentbug fix · easy · 8 min · practice plan

   The callback is given the count but never uses it.

   Passes when: #out should show 1-2-3.

9. 9.Fix the inverted filterbug fix · easy · 8 min · practice plan

   The condition keeps the wrong numbers.

   Passes when: #out should show 8,12.

10. 10.Fix the callback that returns nothingbug fix · easy · 8 min · practice plan

    Without a return the collected values are all undefined.

    Passes when: #out should show 1,4,9,16.

Between them these tasks cover Callbacks, Passing functions and Callback arguments.

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