Kwatanta callbacks, Promises da async/await.

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Accepted Answer

Waɗannan sune jiʼu uku na shaƙaƙa al'amurukan **asynchronous** a Node — kowanné yana gida karantawa jiya, amma dukkansu an gina su akan tushen event-loop.

## 1. Callbacks — asali (da "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);
    });
  });
});
```

Gagawan Node shine **error-first callbacks** (`(err, result)`). Suna aiki amma suna takala zurfafa kuma suna yajjiye shatuwa — wuya wajen karantawa da kiyaye.

## 2. Promises — chainable, flatter

```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
```

Promise yayi wakilci ga ƙimar gida; `.then` yana tuƙi mataki da `.catch` yayi shatuwar kowane abu a jerin — flatter fiye da nested callbacks.

## 3. async/await — synchronous-looking (mabangare na zamani)

```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` shine syntactic sugar akan Promises — yana karantawa daga saman zuwa ƙasan kamar sync code, yana amfani da ordinary `try/catch`, kuma shine mabangare da aka ce dole a zamani.

## Kar a serialize aiki mai zaman kansa

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

## Alaka

```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.
```

## Yanda ya dace

Async handling ba zai iya gudhe a Node (duk I/O ba ya iya juyawa).
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