nextjs-app-router-patterns

# Next.js App Router Patterns Comprehensive patterns for Next.js 14+ App Router architecture, Server Components, and modern full-stack React development. ## When to Use This Skill - Building new Next.js applications with App Router - Migrating from Pages Router to App Router - Implementing Server Components and streaming - Setting up parallel and intercepting routes - Optimizing data fetching and caching - Building full-stack features with Server Actions ## Core Concepts ### 1. Rendering Modes | Mode | Where | When to Use | | --------------------- | ------------ | ----------------------------------------- | | **Server Components** | Server only | Data fetching, heavy computation, secrets | | **Client Components** | Browser | Interactivity, hooks, browser APIs | | **Static** | Build time | Content that rarely changes | | **Dynamic** | Request time | Personalized or real-time data | | **Streaming** | Progressive | Large pages, slow data sources | ### 2. File Conventions ``` app/ ├── layout.tsx # Shared UI wrapper ├── page.tsx # Route UI ├── loading.tsx # Loading UI (Suspense) ├── error.tsx # Error boundary ├── not-found.tsx # 404 UI ├── route.ts # API endpoint ├── template.tsx # Re-mounted layout ├── default.tsx # Parallel route fallback └── opengraph-image.tsx # OG image generation ``` ## Quick Start ```typescript // app/layout.tsx import { Inter } from 'next/font/google' import { Providers } from './providers' const inter = Inter({ subsets: ['latin'] }) export const metadata = { title: { default: 'My App', template: '%s | My App' }, description: 'Built with Next.js App Router', } export default function RootLayout({ children, }: { children: React.ReactNode }) { return ( <html lang="en" suppressHydrationWarning> <body className={inter.className}> <Providers>{children}</Providers> </body> </html> ) } // app/page.tsx - Server Component by default async function getProducts() { const res = await fetch('https://api.example.com/products', { next: { revalidate: 3600 }, // ISR: revalidate every hour }) return res.json() } export default async function HomePage() { const products = await getProducts() return ( <main> <h1>Products</h1> <ProductGrid products={products} /> </main> ) } ``` ## Detailed patterns and worked examples Detailed pattern documentation lives in `references/details.md`. Read that file when the navigation tier above is insufficient. ## Best Practices ### Do's - **Start with Server Components** - Add 'use client' only when needed - **Colocate data fetching** - Fetch data where it's used - **Use Suspense boundaries** - Enable streaming for slow data - **Leverage parallel routes** - Independent loading states - **Use Server Actions** - For mutations with progressive enhancement ### Don'ts - **Don't pass serializable data** - Server → Client boundary limitations - **Don't use hooks in Server Components** - No useState, useEffect - **Don't fetch in Client Components** - Use Server Components or React Query - **Don't over-nest layouts** - Each layout adds to the component tree - **Don't ignore loading states** - Always provide loading.tsx or Suspense