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

#57
30min

Invoker Modal

Not every interaction needs React state. The browser can open and close a dialog with plain HTML attributes via the Invoker Commands API — no useState, no event handlers, no JavaScript.

ddd
dialognative apis
#58
15min

useEffect vs useLayoutEffect

A tooltip must center itself by measuring its width. Change useEffect for useLayoutEffect — one line, but it makes the difference between a visible flicker and a perfect first frame.

ddd
useEffectuseLayoutEffectuseRef
#59
30min

GitHub Contribution Heatmap

Fetch contribution data for a GitHub-style heatmap using SWR. The grid and components are already built — your job is to wire up data fetching with loading skeletons, error handling, and year navigation to bring the heatmap to life.

ddd
useStatefetchingSWR

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