Mastering TypeScript: Advanced Patterns for Better Code

TypeScript has evolved far beyond a simple type checker. Modern TypeScript offers powerful type-level programming capabilities that can help you write more robust, maintainable code.

Conditional Types

Conditional types allow you to create types that depend on a condition:

type ApiResponse<T> = T extends string 
  ? { message: T } 
  : { data: T };

type StringResponse = ApiResponse<string>; // { message: string }
type UserResponse = ApiResponse<User>; // { data: User }

Mapped Types

Transform existing types by mapping over their properties:

type Partial<T> = {
  [P in keyof T]?: T[P];
};

type Required<T> = {
  [P in keyof T]-?: T[P];
};

Template Literal Types

Create string types with specific patterns:

type EventName<T extends string> = `on${Capitalize<T>}`;

type ClickHandler = EventName<'click'>; // 'onClick'
type HoverHandler = EventName<'hover'>; // 'onHover'

Utility Types in Practice

Combine utility types for powerful transformations:

interface User {
  id: number;
  name: string;
  email: string;
  password: string;
}

type PublicUser = Omit<User, 'password'>;
type UserUpdate = Partial<Pick<User, 'name' | 'email'>>;

Best Practices

1. Start Simple: Begin with basic types and gradually add complexity
2. Use Utility Types: Leverage built-in utilities before creating custom ones
3. Type Guards: Implement proper runtime type checking
4. Generic Constraints: Use constraints to make generics more specific

Conclusion

Advanced TypeScript patterns enable you to catch more errors at compile time and create more expressive APIs. Master these patterns to take your TypeScript skills to the next level.