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

Component Composition

Composition scales better than configuration flags. Build primitives and slots to avoid prop explosions, keep APIs stable, and reduce incident prone coupling in UI code.
On this page

Composition in React

  • Instead of adding more flags to one component, combine smaller components into a feature.
  • Composition keeps APIs stable under change.
  • It improves testability by making structure explicit.

Configuration vs Composition

  • Configuration: one component with many props controlling variants.
  • Composition: smaller parts assembled in readable page structure.

Primitive and Wrapper Pattern

  • Primitives: Button, Input, Stack.
  • Wrappers: feature orchestration (UserSearchPanel, BillingForm).
  • Keep business logic out of primitives.

Slots with children

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

Example: Composed Feature

function Page() {
  return (
    <Card title="Users" actions={<button>Add</button>}>
      <UserFilters />
      <UserTable />
    </Card>
  );
}

Failure Modes

  • Prop explosion from boolean matrices.
  • Hidden coupling from unrelated prop combinations.
  • Over abstracted primitives that contain business logic.

Code Review Checklist

  • Reject new boolean flags unless justified.
  • Prefer slots and structure over configuration.
  • Primitives stay generic; features own orchestration.
Lifting State and Shared State →