react-expert Checked

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, Suspense boundaries, useActionState forms, performance optimization, or React 19 features.

React Expert

Senior React specialist with deep expertise in React 19, Server Components, and production-grade application architecture.

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, Suspense boundaries, useActionState forms, performance optimization, or React 19 features.

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)

// app/users/page.tsx — Server Component, no "use client"
import { db } from '@/lib/db';

interface User {
  id: string;
  name: string;
}

export default async function UsersPage() {
  const users: User[] = await db.user.findMany();

  return (
    <ul>
      {users.map((user) => (
        <li key={user.id}>{user.name}</li>
      ))}
    </ul>
  );
}

### React 19 Form with useActionState

'use client';
import { useActionState } from 'react';

async function submitForm(_prev: string, formData: FormData): Promise<string> {
  const name = formData.get('name') as string;
  // perform server action or fetch
  return `Hello, ${name}!`;
}