Utility Types

Code

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

type PartialUser = Partial<User>;          // All properties optional
type RequiredUser = Required<User>;        // All properties required
type ReadonlyUser = Readonly<User>;        // All properties readonly
type PickUser = Pick<User, "id" | "name">; // Pick some properties
type OmitUser = Omit<User, "email">;       // Omit some properties
type RecordUser = Record<"a" | "b", User>; // Key-value type
type NameType = ReturnType<() => string>;  // Function return type
type Params = Parameters<(a: number, b: string) => void>;

Explanation

TS built-in utility types simplify common type transformations.

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