TypeScript Best Practices for Frontend Development

Why TypeScript?

TypeScript has become the standard for serious JavaScript development. It provides type safety, better tooling, and improved developer experience.

Essential Type Patterns

Interface vs Type

Use interfaces for objects and types for unions:

// Interfaces for object shapes
interface User {
  id: string;
  name: string;
  email: string;
}

// Types for unions and complex types
type Status = 'loading' | 'success' | 'error';
type ApiResponse<T> = { data: T } | { error: string };

Generic Types

Generics make your code reusable while maintaining type safety:

// Generic function
function getFirstItem<T>(items: T[]): T | undefined {
  return items[0];
}

// Generic component props
interface ListProps<T> {
  items: T[];
  renderItem: (item: T) => React.ReactNode;
}

Strict Mode Settings

Enable strict mode in your tsconfig.json:

{
  "compilerOptions": {
    "strict": true,
    "noImplicitAny": true,
    "strictNullChecks": true,
    "noUncheckedIndexedAccess": true
  }
}

Type Guards

Use type guards for runtime type checking:

function isUser(value: unknown): value is User {
  return (
    typeof value === 'object' &&
    value !== null &&
    'id' in value &&
    'name' in value
  );
}

// Usage
if (isUser(data)) {
  console.log(data.name); // TypeScript knows data is User
}

Utility Types

Master these built-in utility types:

Type	Purpose
Partial<T>	All properties optional
Required<T>	All properties required
Pick<T, K>	Select specific properties
Omit<T, K>	Exclude specific properties
Record<K, V>	Object with typed keys/values

Error Handling

Create typed error handling:

class AppError extends Error {
  constructor(
    message: string,
    public code: string,
    public statusCode: number = 500
  ) {
    super(message);
    this.name = 'AppError';
  }
}

// Usage
throw new AppError('User not found', 'USER_NOT_FOUND', 404);

Conclusion

TypeScript is an investment that pays dividends in code quality, maintainability, and developer productivity. Start strict and stay strict!