Mastering React: Best Practices for 2025

Modern React in 2025

React 19 introduces Server Components, Actions, and improved concurrency. Here are the best practices for building performant, maintainable applications.

1. Server Components by Default

// app/page.tsx - Server Component by default
async function Page() {
  const data = await db.query('SELECT * FROM posts');
  return ;
}

Only use 'use client' when you need interactivity (hooks, browser APIs).

2. Use Server Actions for Mutations

'use server';

export async function createPost(formData: FormData) {
  const title = formData.get('title');
  await db.insert('posts', { title });
  revalidatePath('/posts');
}

Eliminates API routes for simple mutations. Works with progressive enhancement.

3. Suspense for Data Fetching

}>
  

Streaming SSR with granular loading states. No more waterfall requests.

4. Compound Components Pattern

const Tabs = ({ children, defaultIndex = 0 }) => {
  const [active, setActive] = useState(defaultIndex);
  return (
    
      
{children}
    
  );
};

Flexible APIs that prevent prop drilling and improve composability.

5. Custom Hooks for Logic Reuse

function useLocalStorage(key, initialValue) {
  const [value, setValue] = useState(() => {
    const stored = localStorage.getItem(key);
    return stored ? JSON.parse(stored) : initialValue;
  });

  useEffect(() => {
    localStorage.setItem(key, JSON.stringify(value));
  }, [key, value]);

  return [value, setValue];
}

6. Performance Optimization

• React.memo for expensive components
• useMemo/useCallback for stable references
• Virtualize long lists with @tanstack/react-virtual
• Code-split with React.lazy and Suspense

7. State Management: Less is More

• Local state: useState, useReducer
• Shared state: Context + useReducer
• Global state: Zustand, Jotai (lightweight)
• Server state: TanStack Query (React Query)

8. TypeScript Best Practices

interface Props {
  // Prefer interfaces for public APIs
  onSubmit: (data: FormData) => Promise;
  // Discriminated unions for variants
  variant: 'primary' | 'secondary' | 'ghost';
}

9. Testing Strategy

• Unit: Custom hooks, utilities (Vitest)
• Component: React Testing Library
• Integration: User flows, API mocking (MSW)
• E2E: Critical paths only (Playwright)

10. Accessibility by Default

• Semantic HTML always
• ARIA labels only when necessary
• Focus management in modals/drawers
• Color contrast ratios (WCAG AA)
• Test with screen readers