Advanced TypeScript

Utility Types

TypeScript utility types are standard reusable transformations such as Partial, Required, Pick, Omit, Record, ReturnType, Parameters, Extract, Exclude, NonNullable, and Awaited.

Utility types encode common transformations
Pick/Omit are shape tools, not DTO design strategy
Partial is easy to overuse
Record is useful for dictionaries with known key sets
ReturnType and Parameters couple to implementation

Common utility types
Utility	Meaning	Example use
Partial<T>	All properties optional	Draft/update object
Required<T>	All properties required	Normalized config
Pick<T, K>	Keep selected properties	Preview DTO
Omit<T, K>	Remove selected properties	Public shape without secret
Record<K, T>	Map keys to values	Handler table
ReturnType<F>	Function return type	Wrapper/helper
Extract<T, U>	Keep union members assignable to U	Filter variants
Exclude<T, U>	Remove union members assignable to U	Filter variants

Handler table with Record

type Status = "idle" | "loading" | "success" | "error"

type Handler = () => void

const handlers: Record<Status, Handler> = {
  idle: () => {},
  loading: () => {},
  success: () => {},
  error: () => {},
}

Adding a new status forces the table to be updated.