TypeScript Academy · Lesson

Interfaces vs Type Aliases

Compare interfaces and type aliases: both can describe shapes, but they differ in extension, merging, and advanced cases.

Intro

Goal: Understand when to use interfaces vs type aliases. Both describe shapes, but they differ in features and use cases.

Interfaces declare object shapes, can extend other interfaces, and support merging across declarations.

interface User {
  id: number;
  name: string;
}

const u: User = { id: 1, name: "Ada" };