TypeScript Patterns I Use Every Day

After years of writing TypeScript, these are the patterns I reach for most often.

1. Discriminated Unions

Perfect for handling different states in your application:

type AsyncState<T> =
  | { status: 'idle' }
  | { status: 'loading' }
  | { status: 'success'; data: T }
  | { status: 'error'; error: Error };

2. Branded Types

Add type safety to primitive values:

type UserId = string & { __brand: 'UserId' };
type PostId = string & { __brand: 'PostId' };

3. Const Assertions

Get literal types from objects:

const ROUTES = {
  home: '/',
  about: '/about',
} as const;

4. Utility Types

Master the built-in utility types like Pick, Omit, Partial, and Required.

These patterns have saved me countless hours of debugging and made my code more maintainable.