React + TypeScript Integration

Definition: React TypeScript is the practice of building React applications using TypeScript, a strongly-typed superset of JavaScript that adds static type checking, enabling early error detection, better IDE support, and improved code maintainability in enterprise applications.

Why TypeScript + React for Enterprise

TypeScript transforms React development by catching errors at compile time instead of runtime. For enterprise projects serving thousands of users daily, this difference is critical—a type error caught during development costs minutes; the same error in production costs hours and damages user trust.

Key benefits for enterprise React development:

  • Type safety: Props interfaces, state types, and API contracts prevent invalid data from propagating through components
  • Refactoring confidence: Rename functions or change prop structures across 100+ files without fear of breaking production
  • Developer experience: IntelliSense autocomplete, inline documentation, and instant error feedback in VS Code
  • Team collaboration: Explicit interfaces serve as living documentation, making code readable for developers joining 6 months later
  • Enterprise requirements: Major corporations mandate TypeScript for mission-critical systems (all 7 of my enterprise portals use TypeScript)

Setup & Configuration

TypeScript Configuration (tsconfig.json):

{
  "compilerOptions": {
    "target": "ES2020",
    "lib": ["ES2020", "DOM", "DOM.Iterable"],
    "jsx": "react-jsx",
    "module": "ESNext",
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true
  }
}

Key settings for enterprise projects: Enable strict: true (includes strictNullChecks, noImplicitAny, strictFunctionTypes), use path mapping for clean imports, enable noUnusedLocals and noUnusedParameters to keep code clean.

Component Typing Patterns

1. Functional Components with Props:

interface ButtonProps {
  label: string;
  onClick: () => void;
  variant?: 'primary' | 'secondary';
  disabled?: boolean;
}

const Button: React.FC<ButtonProps> = ({ label, onClick, variant = 'primary', disabled }) => {
  return <button onClick={onClick}>{label}</button>;
};

2. Custom Hooks with TypeScript:

function useApi<T>(url: string): { data: T | null; loading: boolean; error: Error | null } {
  const [data, setData] = useState<T | null>(null);
  // ... fetch logic
  return { data, loading, error };
}

3. Event Handlers:

const handleChange = (event: React.ChangeEvent<HTMLInputElement>) => {
  console.log(event.target.value);
};

const handleClick = (event: React.MouseEvent<HTMLButtonElement>) => {
  event.preventDefault();
};

Advanced Patterns

Generic Components

Create reusable components that work with any data type. Example: DataTable<User> vs DataTable<Product> with full type safety for columns and row data.

Discriminated Unions

Model complex state machines where different states have different data shapes. Used extensively in O2 ticket workflows and MONETA loan stages.

Utility Types

Leverage Pick, Omit, Partial, Required to derive types from existing interfaces. Reduces duplication and keeps types DRY.

Type Guards

Narrow union types with custom type predicates. Essential for safely handling API responses and user inputs.

Common Pitfalls & Solutions

  1. Overusing 'any': Avoid the 'any' type escape hatch. Use 'unknown' for truly unknown data, then narrow with type guards. Enable noImplicitAny.
  2. Type Assertions: Minimize 'as' assertions—they bypass type checking. Prefer type guards and proper inference. Use only when you have information TypeScript doesn't.
  3. Missing Library Types: Install @types packages for third-party libraries. If types don't exist, declare minimal interfaces rather than using 'any'.
  4. Complex Generics: Keep generic constraints simple. If a type signature requires 5 type parameters, consider refactoring the component.
  5. Ignoring strictNullChecks: Enable from day one. Retrofitting null safety into a large codebase is painful (learned from migrating Cool Credit lending system).

Real Implementation: TESCO Operations Portal

The TESCO Stores CZ portal uses TypeScript across 40+ components, 15+ custom hooks, and 20+ API integration functions. Strict mode caught 30+ potential runtime errors during refactoring, preventing production bugs.

Key TypeScript wins:

  • Campaign planning forms with multi-step validation: TypeScript interfaces ensure each step receives correctly-shaped data
  • Java REST API integration: Generated TypeScript types from OpenAPI specs guarantee frontend-backend contract alignment
  • Redux state management: Strongly-typed actions and reducers prevent invalid state mutations
  • Material UI customization: Theme type augmentation provides autocomplete for custom color tokens

Tooling & IDE Setup

ESLint TypeScript Rules:

  • @typescript-eslint/no-explicit-any - ban 'any' usage
  • @typescript-eslint/strict-boolean-expressions - prevent loose boolean checks
  • @typescript-eslint/no-unnecessary-type-assertion - remove redundant casts

VS Code Extensions:

  • TypeScript IntelliSense (built-in) for autocomplete and error highlighting
  • Prettier for consistent code formatting
  • Error Lens to display TypeScript errors inline

Related Vocabulary

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