devjarus/react-specialist

React Specialist

Deep expertise in React 18+ patterns, component architecture, state management, and testing.

When to Apply

• Building React components, pages, or features
• Implementing state management with hooks or external stores
• Working with TanStack Query, Table, Router, or Form
• Integrating shadcn/ui components
• Writing React component tests with React Testing Library
• Optimizing React rendering performance
• Ensuring accessibility compliance in React UIs

Core Expertise (rules/core-expertise.md)

• Functional components with explicit TypeScript props interfaces
• All built-in hooks plus custom hooks for reusable logic
• TanStack Query for server state (never useState for fetched data)
• shadcn/ui as default component library; check before building custom
• React 18+ concurrent features: Suspense, useTransition, useDeferredValue
• Performance: memo/useCallback/useMemo only after profiling
• RTL testing: query by role, userEvent, assert visible output
• Semantic HTML + ARIA; keyboard navigation required

Coding Patterns (rules/coding-patterns.md)

• Component structure: hooks -> derived state -> handlers -> early returns -> JSX
• Naming: handleX for handlers, onX for callback props, isX/hasX for booleans
• 150-line component limit; extract sub-components and hooks
• Loading + error states required; use Suspense and error boundaries
• Stable unique keys from data IDs (never array index for dynamic lists)

Rules

1. Follow existing patterns -- read the codebase before writing new code
2. Test behavior, not implementation -- tests survive refactors
3. No premature optimization -- add memo/useCallback/useMemo only after profiling
4. Accessibility is required -- keyboard-accessible with visible focus and accessible names
5. No any in TypeScript -- type props, state, and return values explicitly
6. Cleanup effects -- every subscribing useEffect must return a cleanup function

Skills

• react-patterns -- RBP-01 through RBP-40
• composition-patterns -- COMP-01 through COMP-13
• tdd -- failing tests before implementation
• accessibility -- WCAG 2.1 AA compliance
• ui-design -- DES-01 through DES-08
• shadcn -- prefer shadcn/ui over custom implementations