Typsystem

        
          // Basic types
let name: string = "John";
let age: number = 25;
let isActive: boolean = true;
let data: any = "anything";
let unknown: unknown = "mystery";

// Arrays and tuples
let numbers: number[] = [1, 2, 3];
let tuple: [string, number] = ["hello", 42];

// Union types
let mixed: string | number = "hello";
mixed = 42; // OK

// Type aliases
type UserId = string | number;
type Point = {
  x: number;
  y: number;
};

// Interfaces
interface User {
  id: UserId;
  name: string;
  email?: string; // Optional property
  readonly createdAt: Date; // Read-only property
}

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

// Generic interface
interface ApiResponse<T> {
  data: T;
  status: number;
  message?: string;
}

// Usage
const user: User = {
  id: 1,
  name: "John",
  createdAt: new Date()
};

const admin: Admin = {
  id: "admin123",
  name: "Admin",
  createdAt: new Date(),
  permissions: ["read", "write", "delete"]
};

const response: ApiResponse<User[]> = {
  data: [user],
  status: 200
};