Apa iku union lan intersection types?

Question

Accepted Answer

A **union** (`A | B`) tegese "salah siji A **utawa** B." An **intersection** (`A & B`) tegese "loro A **lan** B ing sawijining wektu."

```ts
// Union — value is one of several types
type Status = "loading" | "success" | "error"; // string literal union
let s: Status = "loading"; // only these three allowed

function id(x: string | number) { /* x is string OR number */ }
```

## Makarya karo unions: sampeyan mung bisa nggunakake sing umum

```ts
function format(x: string | number) {
  // x.toFixed(2); // ❌ toFixed doesn't exist on string
  if (typeof x === "number") return x.toFixed(2); // ✅ narrowed to number
  return x.toUpperCase();                          // ✅ here it's a string
}
```

Sampe sampeyan **narrow** sawijining union, sampeyan mung bisa ngakses anggota sing ana ing *saben* anggota saka union — compiler njaga sampeyan.

## Intersection — gabungake bentuk-bentuk

```ts
type Name = { name: string };
type Age = { age: number };
type Person = Name & Age; // must have BOTH name and age

const p: Person = { name: "Ann", age: 30 }; // both required
```

Intersections bagus kanggo nyusun/nggabungake tipe obyek (contone, nambahake props marang tipe sing wis ana).

## Kenapa iku pentinge

Unions model "salah siji saka pirang-pirang kemungkinan" — fondasi saka state modeling sing aman (contone discriminated unions kanggo reducer state), function overloads, lan nullable types (`T | null`).

Intersections nggabungake tipe-tipe bebarengan.

Saktine loro-lorone, padha ngajaake TypeScript kang sistem tipe cukup expressive kanggo ngreca data nyata kanthi tepat.