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
- Start Simple: Begin with basic types and gradually add complexity
- Use Utility Types: Leverage built-in utilities before creating custom ones
- Type Guards: Implement proper runtime type checking
- 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.