Interfaces

Interfaces are very similar to types and sometimes developers don’t know the differences between them. Interfaces can be used to describe the shape of an object or function signature just like types, but the syntax is different:

interface User {
  username: string
  email: string
  name: string
  age?: number
  website: string
  active: boolean
}

You can name an interface as you want, but a good practice to follow is to add a prefix of I. For example, the User interface will become IUser. In this way, you can quickly recognize that it is an interface, and you don’t get confused thinking it is a class or a React component.

An interface can also be extended, implemented, and merged.