Core Code
Core Code Modern Dev Handbook
REACT Contents
React Fundamentals
React Architecture Overview JSX and Rendering Model Component Design Principles Props and Data Flow State Management with useState Side Effects with useEffect Event Handling Patterns Conditional Rendering Strategies Lists, Keys, and Reconciliation Forms and Controlled Components Component Composition Lifting State and Shared State Basic Routing with React Router Failure Modes in Beginner React Apps
React + TypeScript
Typing Functional Components Typing Props and Children useState and Type Inference useReducer with Type Safety Typing Event Handlers Generic Components Utility Types in React Discriminated Unions for UI State Strict Mode and Null Safety API Response Typing Strategies Form Typing Patterns Avoiding any and Unsafe Casts Type-Safe Context API Failure Modes in React + TypeScript
React Advanced Patterns
Custom Hooks Architecture Context vs Prop Drilling Tradeoffs Compound Components Pattern Controlled vs Uncontrolled Abstractions Render Props and Pattern Alternatives State Machines in React Performance Optimization Playbook Memoization Strategies Code Splitting and Lazy Loading Error Boundaries and Recovery Portal Architecture Large Scale Folder Structure Testing Strategy: Unit and Integration Common React Anti Patterns
React Production
CSR vs SSR vs SSG Hydration and Mismatch Failures Next.js Architecture Overview App Router Deep Dive Authentication Patterns Token Storage Security Role Based UI Control API Integration Patterns Rate Limiting and UI Resilience Frontend Security Checklist XSS in Modern React Observability in Frontend Bundle Optimization Production Incident Playbook
Distributed Systems
Distributed System Fundamentals CAP Theorem in Practice Consistency Models Replication Strategies Leader Election Concepts Consensus Algorithms Overview Event Driven Architectures Message Queues and Delivery Guarantees Idempotency Patterns Saga Pattern Circuit Breakers Backpressure and Flow Control Observability in Distributed Systems Failure Scenarios and Postmortems

Code Splitting and Lazy Loading

Reduce initial bundle size with route level and component level splitting. Learn React.lazy, Suspense boundaries, loading strategies, and production risks like waterfalls and error boundary gaps.
On this page

Why Code Splitting Matters

  • Large bundles delay first interaction.
  • Users rarely need the entire application on first load.
  • Split by route and by heavy feature modules.

Route Level Splitting

  • Lazy load page components.
  • Keep layout shell eagerly loaded.
  • Prefetch likely next routes when idle.

Example: React.lazy

const AdminPage = React.lazy(() => import("./AdminPage"));

function App() {
  return (
    <React.Suspense fallback={<Spinner />}>
      <AdminPage />
    </React.Suspense>
  );
}

Suspense Boundary Design

  • Place boundaries around slow loading regions.
  • Avoid wrapping entire app in one Suspense.
  • Combine with error boundaries to catch load failures.

Prefetch Strategy

  • Prefetch when link is visible or hovered.
  • Prefetch based on user navigation patterns.
  • Avoid overfetching large chunks unnecessarily.

Failure Modes

  • Waterfall loading due to nested lazy imports.
  • Single Suspense boundary blocking entire UI.
  • Missing error boundaries causing blank screens.
  • Chunk duplication from misconfigured bundler.

Deployment Checklist

  • Analyze bundle size after build.
  • Verify chunk caching headers.
  • Ensure fallback UI is meaningful.
  • Test slow network simulation.
Error Boundaries and Recovery →