Typescript - Utility Types

Partial

Makes all properties of a type optional

type Product = {
	id: string;
	name: string; 
	supplier: string;
}
 
// ID is optional
const updatedProduct: Partial<Product> = {
	name: "Salt",
	supplier: "The Saltworks"
}

Required

Makes all properties of a type required

type Contact = {
	id: string;
	name: string; 
	address?: string;
}
 
const newContact: Required<Contact> = {
	id: "01",
	name: "Max",
	address: "Sample-Street 5"
}

Readonly

Prevents values from this type to be reassigned

type ServerConfig = {
	endpoint: string
}
 
const config: Readonly<ServerConfig> = {
	endpoint: "http://sample.com"
}
 
config.endpoint = 'http://yoink.com' // throws an error

Pick

Creates a new type from a subset of another interface / type

type User = {
	id: string; 
	name: string;
	email: string;
	address: {
		city: string;
		street: string;
		houseNumber: number
	}
}
 
type CreateuserDTO = Pick<User, "name" | "email">

Omit

Creates a new type without a subset of another interface / type

type ClimatedBus = {
	name: string;
	model: string;
	climate: boolean;
}
 
type Bus = Omit<ClimatedBus, "climate">

Record

Type with a set of properties and values. Useful to create dynamic objects or maps

type User = { 
	id: string; 
	name: string;
}
 
type UserHashmap = Record<string, User>
 
// Alternatively create the User type with a Record
type UserKeys = "id" | "name";
type UserRecord = Record<UserKeys, string>

Parameters

Extracts the types of function arguments as a tuple

function greet(name: string, language: "DE" | "EN") {
	// ...
}
 
type greetArgs = Parameters<typeof greet>