avatarSlavo_3, July 26, 2022

Interfaces and Types in TS

There are two different ways now how you can specify the structure of your data.

TODO: provide alt

There are two different ways in TypeScript how you can specify the structure of your data.

We can use Interface and Types.

They are very similar, almost everything you can do with the Interface, you can also do with the Type.

In TypeScript is recommended to use Interface over Type alias when it's possible.

The interface describes data structure in a more natural way.

Interface keyword exists only in TypeScript non in vanilla JavaScript. It is helping us to write structured and very explicit code that can help you force classes to have certain features or objects in general to have a specific structure. They allow for optional properties and all optional methods if you add a question mark after the method name.

You can't assign a default value inside the Interface, just the property's name, and type.

interface User {
    username: string
    project: string
    years: number

    hello?(name: string): void 

  const userOne: User = {
    username: "slavo3dev",
    project: "NRG Nomad",
    years: 1

Type Alias

type Username = string
type PersonLogFunction = (name: string) =>  string 

const username: string = "Slavo_3"

const logUser: PersonLogFunction = (name) => {
    return name;

const firstUser: Username = logUser(username)