TypeScript Fundamentals

// Primitives
const name: string = "Alice";
const age: number = 25;
const active: boolean = true;

// Arrays
const numbers: number[] = [1, 2, 3];
const strings: Array<string> = ["a", "b"];

// Union types
const id: string | number = 123;

// Any (avoid when possible)
let data: any = "anything";

// Interface
interface User {
  name: string;
  age: number;
  email?: string;  // Optional
}

// Type alias
type UserRole = "admin" | "user" | "guest";

// Using them
const user: User = {
  name: "Alice",
  age: 25
};

const role: UserRole = "admin";

// Function with types
const add = (a: number, b: number): number => {
  return a + b;
};

// Function with optional parameters
const greet = (name: string, greeting: string = "Hello"): string => {
  return `${greeting}, ${name}`;
};