Async/await inafanya kazi vipi?

Question

Accepted Answer

`async/await` ni **syntax sugar juu ya Promises** inayokupa kufanya kod kisimu ambayo inaonekana kama kod ya synchronous. Kazi ya `async` kila wakati inarudisha Promise; `await` inasimamisha kazi hadi Promise isettli, kisha inaendelea na thamani yake.

```js
async function loadUser(id) {
  try {
    const res = await fetch(`/api/users/${id}`); // pause until the response
    const user = await res.json();               // pause until parsed
    return user;                                  // becomes the resolved value
  } catch (err) {
    console.error(err); // catches rejections from any await above
  }
}
```

## Mfululizo vs sambamba — kosa la kawaida la utendaji

`await` inafanya kazi **moja baada ya nyingine**. Ikiwa ombi mbili hazitegemei kila mmoja, kusubiri zao kwa mfululizo ni kuchozeana kwa muda:

```js
// ❌ sequential — total time = a + b
const a = await getA();
const b = await getB();

// ✅ parallel — total time = max(a, b)
const [a, b] = await Promise.all([getA(), getB()]);
```

## Kupangilia makosa

Tumia `try/catch` badala ya `.catch`. Promise inayokataliwa iliyosubiriwa inatatupa, kwa hivyo `catch` moja inakamatia kizuizi kizima.

## Chini ya mkeka

Bado Promises na microtask queue — `await` haisimamizi thread; inatoa udhibiti ili kod nyingine inatekeleze, kisha inaendelea. Usisahau: kuita kazi ya `async` bila `await`ing (au `.catch`) inaweza kuficha makosa.

## Kwa nini inafaa

Inafanya mtiririko wa async kuwa majibu na ni kiwango kinachomtumia sasa kwa kuandama kazi isiyo na sambamba — lakini lazima ubadilishe kwa makusudi operesheni huru na `Promise.all`.