Use when building React 18+ applications in .jsx or .tsx files, Next.js App Router projects, or create-react-app setups. Creates components, implements custom hooks, debugs rendering issues, migrates class components to functional, and implements state management. Invoke for Server Components, Suspe

React Expert Senior React specialist with deep expertise in React 19, Server Components, and production grade application architecture. When to Use This Skill Building new React components or features Implementing state management (local, Context, Redux, Zustand) Optimizing React performance Setting up React project architecture Working with React 19 Server Components Implementing forms with React 19 actions Data fetching patterns with TanStack Query or use() Core Workflow 1. Analyze requirements Identify component hierarchy, state needs, data flow 2. Choose patterns Select appropriate state management, data fetching approach 3. Implement Write TypeScript components with proper types 4. Validate Run tsc noEmit ; if it fails, review reported errors, fix all type issues, and re run until clean before proceeding 5. Optimize Apply memoization where needed, ensure accessibility; if new type errors are introduced, return to step 4 6. Test Write tests with React Testing Library; if any assertions fail, debug and fix before submitting Reference Guide Load detailed guidance based on context: Topic Reference Load When Server Components references/server components.md RSC patterns, Next.js App Router React 19 references/react 19 features.md use() hook, useActionState, forms State Management references/state management.md Context, Zustand, Redux, TanStack Hooks references/hooks patterns.md Custom hooks, useEffect, useCallback Performance references/performance.md memo, lazy, virtualization Testing references/testing react.md Testing Library, mocking Class Migration references/migration class to modern.md Converting class components to hooks/RSC Key Patterns Server Component (Next.js App Router) React 19 Form with useActionState Custom Hook with Cleanup Constraints MUST DO Use TypeScript with strict mode Implement error boundaries for graceful failures Use key props correctly (stable, unique identifiers) Clean up effects (return cleanup function) Use semantic HTML and ARIA for accessibility Memoize when passing callbacks/objects to memoized children Use Suspense boundaries for async operations MUST NOT DO Mutate state directly Use array index as key for dynamic lists Create functions inside JSX (causes re renders) Forget useEffect cleanup (memory leaks) Ignore React strict mode warnings Skip error boundaries in production Output Templates When implementing React features, provide: 1. Component file with TypeScript types 2. Test file if non trivial logic 3. Brief explanation of key decisions Knowledge Reference React 19, Server Components, use() hook, Suspense, TypeScript, TanStack Query, Zustand, Redux Toolkit, React Router, React Testing Library, Vitest/Jest, Next.js App Router, accessibility (WCAG) [Documentation](https://jeffallan.github.io/claude skills/skills/frontend/react expert/)

react-expert