Piye carane useState hook bisa tindak?

Question

Accepted Answer

`useState` menehi fungsi component sawijining potongan **lokal, reaktif state**. Iki bali sepasang: **nilai saiki** lan fungsi **setter**. Nglilani setter nggaduhake ulang render kanthi nilai anyar.

```jsx
const [count, setCount] = useState(0); // 0 is the initial value
setCount(count + 1);   // value form
setCount(c => c + 1);  // functional form (preferred when based on previous)
```

## Loro bab sing ngejutaken para pemula

**1. Update iku asinkron / dibathik.** `count` ora owah ing baris sawise `setCount`; dheweke duwe nilai anyar ing *render* sabanjure. Dadi iki mung nambah sawiji:

```jsx
setCount(count + 1);
setCount(count + 1); // both read the SAME stale `count` → +1 total
```

Gunakake **functional updater** nalika nilai sabanjure gumantung ing sing sadurunge, amarga React nglilani nilai paling anyar:

```jsx
setCount(c => c + 1);
setCount(c => c + 1); // +2 total — each gets the up-to-date value
```

**2. Nilai awal mung digunakake ing render pertama.** Kanggo default sing larang, nerangake fungsi supaya bisa mlayu sepisan (lazy init):

```jsx
const [data] = useState(() => expensiveInit()); // runs once, not every render
```

## Alasan iki penting

State iku apa sing ndadekake component interaktif — React nglalir maneh fungsi lan nggawe ulang UI mangsho state owah.

Perlakuke state minangka **immutable**: gawa array/object anyar tinimbang ngowahi, cth `setItems([...items, x])`, yen ora React bisa uga ora ketemu owahan.