nextjs-patterns

Next.js Patterns

Comprehensive guide to building production-grade Next.js applications with the App Router, Server Components, and modern React patterns.

Core Architecture

App Router vs Pages Router

Project Structure

my-app/
├── app/
│   ├── layout.tsx          # Root layout
│   ├── page.tsx            # Home page
│   ├── loading.tsx         # Root loading state
│   ├── error.tsx           # Root error boundary
│   ├── not-found.tsx       # 404 page
│   ├── (auth)/             # Route group
│   │   ├── login/page.tsx
│   │   └── register/page.tsx
│   ├── dashboard/
│   │   ├── layout.tsx      # Dashboard layout
│   │   ├── page.tsx        # Dashboard home
│   │   ├── loading.tsx
│   │   └── settings/
│   │       └── page.tsx
│   └── api/
│       └── [...route]/route.ts  # API handlers
├── components/
│   ├── ui/                 # Shared UI components
│   └── features/           # Feature-specific components
├── lib/
│   ├── db.ts              # Database client
│   ├── auth.ts            # Auth utilities
│   └── utils.ts           # Shared utilities
└── public/
    └── images/

Server Components (RSC)

When to Use Server vs Client

// ✅ SERVER COMPONENT (default) — Use for:
// - Data fetching from databases/APIs
// - Accessing backend resources directly
// - Keeping sensitive logic on server
// - Reducing client bundle size
// - SEO-critical content
async function ProductPage({ params }: { params: { id: string } }) {
  const product = await db.product.findUnique({ where: { id: params.id } });
  return <ProductDetail product={product} />;
}

// ✅ CLIENT COMPONENT — Use for:
// - Interactivity (onClick, onChange, etc.)
// - useState, useReducer, useEffect
// - Browser-only APIs
// - Custom hooks
// - Event listeners
'use client';
function AddToCartButton({ productId }: { productId: string }) {
  const [added, setAdded] = useState(false);
  return (
    <button onClick={() => { addToCart(productId); setAdded(true); }}>
      {added ? 'Added!' : 'Add to Cart'}
    </button>
  );
}