When working with objects, you often reuse the same structure in multiple places. Instead of rewriting the type every time, you can create a reusable definition.

Type Aliases

A type alias lets you define a custom type:

type User = {
  name: string;
  age: number;
};

You can now use this type anywhere:

let user: User = {
  name: "Alice",
  age: 30,
};

Interfaces

Interfaces provide another way to define object structure:

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

Used the same way:

let user: User = {
  name: "Bob",
  age: 25,
};

Type vs Interface

At a beginner level, both are very similar.

You can use either one to:

• Define object shapes;
• Reuse data structures;
• Improve readability.

In this track, you can use whichever feels more comfortable.

Arrays with Custom Types

You can also use your types with arrays:

let users: User[] = [
  { name: "Alice", age: 30 },
  { name: "Bob", age: 25 },
];