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 Functional Components

Type props at the boundary and let inference handle returns. Learn stable component contracts, minimal public APIs, and failure modes caused by implicit any and unsafe casts.
On this page

Typing Philosophy

  • Type at boundaries. Props define the public contract.
  • Let TypeScript infer return types unless there is a specific reason to enforce them.
  • Keep component public APIs minimal and stable.

Preferred Pattern

type ButtonProps = {
  label: string;
  onClick: () => void;
  disabled?: boolean;
};

function Button({ label, onClick, disabled }: ButtonProps) {
  return (
    <button onClick={onClick} disabled={disabled}>
      {label}
    </button>
  );
}

Why Not React.FC

  • React.FC implicitly adds children even when not intended.
  • It hides explicit control over return type and generics.
  • Explicit function typing improves clarity and long term maintainability.

Boundary Discipline

  • Never allow implicit any at component boundaries.
  • Validate external data before assigning to typed props.
  • Avoid widening types unnecessarily.

Failure Modes

  • Implicit any leaking into the component tree.
  • Overly broad types allowing invalid states.
  • Unsafe type assertions masking runtime bugs.
  • Public prop types changing frequently and breaking consumers.

Code Review Checklist

  • Props are explicitly typed.
  • No any at component boundary.
  • No unnecessary type assertions.
  • Public API surface is minimal.
Typing Props and Children →