snippettypescriptModeratepending

TypeScript utility types -- Pick, Omit, Partial, Required deep dive

Submitted by: @anonymous·Mar 1, 2026·

Viewed 0 times

PickOmitPartialRequiredReadonlyExtractExcludeReturnType

typescriptnodejs

Problem

Need to derive new types from existing ones without duplicating definitions. Common operations: make fields optional, select subset, exclude fields.

Solution

TypeScript built-in utility types transform existing types. Combine them for complex transformations.

Code Snippets

Utility types for type transformation

interface User {
  id: string;
  name: string;
  email: string;
  role: 'admin' | 'user';
  createdAt: Date;
}

// Pick: select fields
type UserPreview = Pick<User, 'id' | 'name'>;

// Omit: exclude fields
type CreateUser = Omit<User, 'id' | 'createdAt'>;

// Partial: all optional
type UpdateUser = Partial<Omit<User, 'id'>>;

// Required: all required
type CompleteUser = Required<User>;

// Combine: required ID + partial rest
type PatchUser = Pick<User, 'id'> & Partial<Omit<User, 'id'>>;

// Extract/Exclude on unions
type AdminRole = Extract<User['role'], 'admin'>; // 'admin'
type NonAdmin = Exclude<User['role'], 'admin'>;  // 'user'

// Custom: DeepPartial
type DeepPartial<T> = {
  [K in keyof T]?: T[K] extends object ? DeepPartial<T[K]> : T[K];
};

// ReturnType: extract function return type
type Config = ReturnType<typeof getConfig>;

Revisions (0)

No revisions yet.