How do you create and use custom types in TypeScript?

In TypeScript, you can create custom types using the keywords type and interface.

• type allows you to create aliases for types, combine types through unions (|) or intersections (&).
• interface is used to describe the structure of objects, classes, and can be extended.

Example of creating a custom type and interface:

// Type alias
type ID = string | number;

// Interface for a user object
interface User {
  id: ID;
  name: string;
  age?: number; // optional property
}

// Usage
const user: User = { id: 123, name: "Ivan" };

function printUser(user: User) {
  console.log(`${user.name} (${user.id})`);
}

printUser(user);

Thus, custom types help describe data structures and provide static typing in the code.