🟦 TypeScript (สอนแบบครบระดับ)

let name: string = 'Somchai';
let age: number = 20;
let isStudent: boolean = true;

let tags: string[] = ['ts', 'types'];
let scores: Array<number> = [10, 20, 30];

// union type
let id: string | number = 'u_1';
id = 123;

// literal type
let status: 'draft' | 'published' = 'draft';

function add(a: number, b: number): number {
  return a + b;
}

const formatName = (firstName: string, lastName: string): string => {
  return firstName + ' ' + lastName;
};

// optional + default
function greet(name?: string) {
  return 'Hi ' + (name ?? 'Guest');
}

function calcVat(price: number, vatRate: number = 0.07) {
  return price * vatRate;
}