Langkah 1: TypeScript — JavaScript + Types

TypeScript menambahkan sistem tipe statis ke JavaScript. Error terdeteksi SEBELUM runtime:

// Type annotation
let nama: string = "Budi"
let umur: number = 17
let lulus: boolean = true
let nilai: number[] = [85, 90, 78]

// Union type
let id: string | number = "abc123"
id = 456  // juga valid

// Literal type
let arah: "kiri" | "kanan" | "lurus" = "kiri"

// Tuple
let koordinat: [number, number] = [10.5, -7.25]

// Optional
let email: string | undefined = undefined

// Type alias
type Nilai = number
type Grade = "A" | "B" | "C" | "D"

const hitungGrade = (n: Nilai): Grade => {
    if (n >= 90) return "A"
    if (n >= 75) return "B"
    if (n >= 60) return "C"
    return "D"
}

Tugasmu: Buat type alias Koordinat (tuple [number, number]), deklarasikan variabel bertipe Koordinat, dan buat fungsi jarak(a: Koordinat, b: Koordinat): number.