Pick<Type, Keys>

INFO

The Pick<Type, Keys> utility type is available starting from TypeScript version 2.1. For more information see in TypeScript Handbook, Release Note.

Overview

Pick<Type, Keys> is a built in utility type in TypeScript that contructs a type by picking the set of properties Keys from Type.

Syntax

type Pick<T, K extends keyof T> = { [P in K]: T[P] };

• Type (T): This is the existing type from which you want to pick specific properties.
• Keys (K): This is a union of string literal types representing the keys of the properties you want to pick from the Type. The keys are combined using the pipe(|) symbol.

Examples

Example #1

interface Task {
  title: string;
  description: string;
  completed: boolean;
}

type TaskPreview = Pick<Task, 'title' | 'completed'>;

const task: TaskPreview = {
  title: 'Clean room',
  completed: false,
};

Example #2

function pick<T extends Record<string, any>, K extends keyof T>(obj: T, keys: K[]): Pick<T, K> {
  const result = {} as Pick<T, K>;

  for (const key of keys) {
    result[key] = obj[key];
  }

  return result;
}

Example #3

interface Credential {
  name: string;
  email: string;
  password: string;
}

class AuthService {
  // Method to create a user account
  async create({ name, email, password }: Credential): Promise<void> {
    // In a real implementation,
    // this would include logic to store the user data in a database.
  }

  // Method to log in a user
  async login({ email, password }: Pick<Credential, 'email' | 'password'>): Promise<void> {
    // In a real implementation,
    // this would include logic to authenticate the user using email and password.
  }

  // Method to log out a user
  async logout({ email }: Pick<Credentail, 'email'>): Promise<void> {
    // In a real implementation,
    // this would include logic to end the user session.
  }
}