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Interfaces

Interfaces describe the shape of objects and can be extended.

Official docs

Object Types — typescriptlang.org

Defining Interfaces​

interface User {
  id: number;
  name: string;
  email?: string; // optional
}

function greet(user: User) {
  return `Hello, ${user.name}`;
}

Extending Interfaces​

interface Admin extends User {
  permissions: string[];
}