Typescript

Choose some properties with Pick

Typescript is very powerful in terms of type checking, but sometimes it gets tedious when some types are subsets of other types and you need to define type checking for them.

Let’s take an example, we have 2 types of response:

interface UserResponse {
  id: number;
  name: string;
  email: string;
  phone: string;
  age: number;
}

interface SignInResponse {
  id: number;
  name: string;
  token: string;
}

Instead of defining types of the same context SignInResponse and UserResponse, we can define the type for UserResponse and choose some properties for SignInResponse. Let’s see:

interface SignInResponse extends Pick<UserResponse, "id" | "name"> {
  token: string;
};

Uppercase / Lowercase

type Role = "admin" | "user" | "guest";
type UppercaseRole = Uppercase<Role>; // "ADMIN" | "USER" | "GUEST"

type Role = "ADMIN" | "USER" | "GUEST";
type LowercaseRole = Lowercase<Role>; // "admin" | "user" | "guest"

Lo mismo sería con Capitalize y Uncapitalize

Optional properties with Partial

Creates a type with all properties of Type set as optional.

interface Product {
  name: string;
  price: number;
  units: number;
}

type PartialProduct = Partial<Product>;

// It's like to do
interface PartialProduct {
  name?: string;
  price?: number;
  units?: number;
}

For the opposite effect is used Required<Product>

Record

interface User {
  id: number;
  name: string;
  lastName: string
}
interface Book {
  createdBy: User;
  updatedBy: User;
}

type BookRecord = Record<"createdBy" | "updatedBy", User>;