Tick three times — practice exercise

What you'll be asked to do

1. 1.Tick three timesexercise · easy · 10 min

   Use setInterval to count to three, then stop and report the count.

   Passes when: #out should show 3.

2. 2.Count downexercise · easy · 10 min · practice plan

   Count down from three and report liftoff at the end.

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

3. 3.Stop after one runexercise · easy · 10 min · practice plan

   Clear the interval inside its own first run.

   Passes when: #out should show ran once.

4. 4.Build a totalexercise · easy · 10 min · practice plan

   Add one each tick until the total reaches five, then report it.

   Passes when: #out should show 5.

5. 5.Repeat with setTimeout insteadexercise · medium · 10 min · practice plan

   Use a repeating setTimeout so each run schedules the next.

   Passes when: #out should show run 3.

6. 6.Fix the interval that never stopsbug fix · easy · 8 min

   Without clearInterval the count keeps rising past three.

   Passes when: #out should show 3.

7. 7.Fix the id not keptbug fix · easy · 8 min · practice plan

   clearInterval needs the id that setInterval returned.

   Passes when: #out should show stopped.

8. 8.Fix setTimeout used where a repeat is neededbug fix · easy · 8 min · practice plan

   setTimeout runs once, so the count never reaches three.

   Passes when: #out should show 3.

9. 9.Fix the countdown ending earlybug fix · easy · 8 min · practice plan

   The interval stops one step too soon.

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

10. 10.Fix the interval cleared before it runsbug fix · easy · 8 min · practice plan

    Clearing it straight away means the callback never fires at all.

    Passes when: #out should show ran once.

Between them these tasks cover setInterval, clearInterval and Repeating work.

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