Live Interactive Demo Model
Countdown Timer & Stopwatch
A precision stopwatch that records lap times and a countdown timer with alarm alerts and presets.
00:00.00
Acceptance Criteria
Using Date.now() timestamp calculations to avoid interval drift
Managing timer pause/resume state with cleanup in useEffect
Calculating and displaying lap split histories
Target APIs & Concepts
Date.now() Drift PreventionsetInterval CleanupLap Recording
Ready to code this yourself? Switch to the Candidate Code Studio to write your implementation in React 19 and run automated test evaluations!