Master React Through Real-World Challenges
Write React and TypeScript in a full Monaco editor with IntelliSense, autocomplete, and optional Vim mode.
Run your code against a real Node + Jest server — the same setup you’d face in production and technical interviews.
Last challenges
#53
20min
Best practices
In a technical interview, solving the logic is only half the battle — reviewers also judge your code's quality. A todo list that works perfectly can still hide anti-patterns like derived state in effects, impure renders, or eager initializers that degrade performance. This challenge is different: instead of just checking that your code passes tests, the platform also runs ESLint with React best-practice rules and surfaces every violation. Fix the 3 lint warnings to prove you don't just make it work — you make it right.
ddduseStateuseEffectESLintbest practices
Simple, transparent pricing
Limited-time offer: enjoy reduced pricing while there are fewer than 100 challenges!
monthly plan
$9/month
Billed monthly
- 1Full access to 50+ challenges across all levels
- 2New challenges added every week
- 3Exclusive advanced topics: Redux, React 19, compound components
- 4View solutions and learn from working code
annual plan
$5/month
Billed $60yearly
save 44%!
- 1Full access to 50+ challenges across all levels
- 2New challenges added every week
- 3Exclusive advanced topics: Redux, React 19, compound components
- 4View solutions and learn from working code
quarterly plan
$7/month
Billed $21quarterly
save 22%!
- 1Full access to 50+ challenges across all levels
- 2New challenges added every week
- 3Exclusive advanced topics: Redux, React 19, compound components
- 4View solutions and learn from working code
FREE
- 1Start solving free coding challenges
- 2All challenges include TypeScript and pre-styled layouts
- 3Code editor with optional Vim mode
- 4Run and test your code instantly in the browser