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

Typing Props and Children

Type children intentionally. Use ReactNode for renderable content, restrict when necessary, and avoid accidental implicit children that break component contracts.
On this page

Typing Children Correctly

  • Use React.ReactNode for generic renderable content.
  • Use stricter types only when enforcing structure.
  • Do not implicitly accept children unless required.

Example: Generic Container

type CardProps = {
  title: string;
  children: React.ReactNode;
};

function Card({ title, children }: CardProps) {
  return (
    <section>
      <h3>{title}</h3>
      {children}
    </section>
  );
}

Example: Render Prop

type ListProps<T> = {
  items: T[];
  render: (item: T) => React.ReactNode;
};

function List<T>({ items, render }: ListProps<T>) {
  return <>{items.map(render)}</>;
}

Common Mistakes

  • Accepting children when component does not use them.
  • Using any for children.
  • Over restricting children and blocking valid use cases.

Failure Modes

  • Unexpected layout injection from implicit children.
  • Hard to reuse components due to overly strict types.
  • Runtime crashes from unsafe assumptions about children shape.

Checklist

  • Children explicitly typed only when needed.
  • No implicit React.FC children behavior.
  • Render props typed explicitly.
useState and Type Inference →