Yaya useState hook ke aiki?

Question

Accepted Answer

`useState` yana ba da ɓangare na aiki ɓangare na **halaye na gida, da jinkiri**. Yana dawo da nau'i: **kimar yanzu** da aiki na **saita**. Kiran saita yana shirya sake juyawa tare da sabon kimar.

```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)
```

## Abubuwa biyu da suka taɓa mamaki wa masu farawa

**1. Sagini ba daidai ba ne / ana damka.** `count` ba ya canza akan layin bayan `setCount`; yana da sabon kimar a *jiya na gida* sake juyawa. Don haka wannan yana dagowa sau ɗaya ne:

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

Sa **functional updater** lokacin da sabon kimar ya dogara kan na gida, saboda React yana damje sabon kimar:

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

**2. Ana amfani da kimar farawa ne kawai a farkon sake juyawa.** Don tsada mai tsada, damje aiki don ya guddu sau ɗaya (lazy init):

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

## Me ya sa haka ya matuhu

Halaye shi ne abin da ya sanya ɓangare da ma'amala — React yana aike da aiki kuma yana sake juyawa UI duk lokacin da halaye ya canja.

Dauki halaye a matsayin **immutable**: saita sabon jirgin/jili a maimakon bada, misali `setItems([...items, x])`, in ba haka ba React bazai gano canja ba.