Bandhingne callbacks, Promises lan async/await.

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Accepted Answer

Iki telu generasi penanganan operasi **asinkron** ing Node — saben-saben nambah kaandalan dibanding sadurunge, nanging kabeh dibangun ana fondasi event-loop sing padha.

## 1. Callbacks — sing asli (lan "callback hell")

```js
fs.readFile("a.txt", (err, a) => {
  if (err) return handle(err);            // error-first callback convention
  fs.readFile("b.txt", (err, b) => {       // nesting deepens with each step...
    if (err) return handle(err);
    db.save(a + b, (err) => {              // "pyramid of doom"
      if (err) return handle(err);
    });
  });
});
```

Konvensi Node yaiku **error-first callbacks** (`(err, result)`). Bisa mulih nanging ana sajeroning nesting lan mbubar penanganan kesalahan — angel diwaca lan dijaga.

## 2. Promises — bisa dirantai, luwih rata

```js
readFile("a.txt")
  .then(a => readFile("b.txt").then(b => a + b)) // return a promise → chain waits
  .then(combined => db.save(combined))
  .catch(handle);                                 // ONE place for all errors
```

Siji Promise mewakili nilai ing mangsa depan; `.then` mrantai langkah-langkah lan `.catch` nangani kesalahan apa wae ing rantai — luwih rata tinimbang callbacks nesting.

## 3. async/await — terlihat sinkron (standar modern)

```js
async function combine() {
  try {
    const a = await readFile("a.txt");   // pause until resolved
    const b = await readFile("b.txt");
    await db.save(a + b);
  } catch (err) {
    handle(err);                          // normal try/catch works
  }
}
```

`async/await` minangka sintaksis gula ing lumayang Promises — diwaca saka ndhuwur menyang ngisor kaya kode sinkron, nganggo `try/catch` biasa, lan iku gaya modern sing direkomendasikake.

## Aja serialisasi pakaryan independen

```js
// ❌ sequential — slow
const a = await getA(); const b = await getB();
// ✅ parallel — both at once
const [a, b] = await Promise.all([getA(), getB()]);
```

## Hubungan

```text
Callbacks → Promises → async/await
All use the event loop. Promises wrap callbacks; async/await wraps Promises.
Modern code: async/await, with Promise.all to parallelize independent ops.
```

## Ora penting

Penanganan asinkron ora bisa disingkiri ing Node (kabeh I/O asinkron).

Pamahaman kemajuane — error-first callbacks (isih umum ing API/perpustakaan lawas), Promises (bisa dirantai), lan async/await (bisa diwaca, standar) — ngidini sampeyan maca basis kode apa wae lan nulis logika asinkron sing bersih.

Ngerteni manawa kabeh iku mekanisme event-loop sing padha ing ngisor, lan aningali kanggo paraleisoake operasi independen karo `Promise.all`, kunci kanggo kode async Node sing bener lan performan.