Je, unatatua vipi hitilafu katika JavaScript, ikiwa ni pamoja na nambari ya async?

Question

Accepted Answer

Hitilafu ya synchronous hutumia **`try/catch/finally`**, na unapaswa `throw` `Error` vitu (si kamba) ili upate stack trace.

```js
try {
  const data = JSON.parse(input);
} catch (err) {
  if (err instanceof SyntaxError) handleBadJson(err);
  else throw err;        // re-throw what you can't handle
} finally {
  cleanup();             // always runs
}
```

## Kwa nini hii ni muhimu

```js
// async/await → wrap awaits in try/catch
async function load() {
  try {
    return await fetch(url).then(r => r.json());
  } catch (err) { showError(err); }
}

// promises → use .catch
fetch(url).then(use).catch(showError);
```

## Mtego wa kawaida: try/catch haifangi async callbacks

```js
try {
  setTimeout(() => { throw new Error("boom"); }, 0); // ❌ NOT caught
} catch (e) { /* never runs — the throw happens later, outside this stack */ }
```

Komandi ya `setTimeout` callback inaendesha kwenye tick baadaye, kwa hivyo `try` inayozunguka imekwisha. Tatua hitilafu *ndani* ya callback.

## Mitandao ya usalama wa kimataifa

```js
window.addEventListener("unhandledrejection", e => log(e.reason)); // browser
process.on("unhandledRejection", err => log(err));                 // Node
```

## Desturi nzuri

- Tupa `Error` (au subclasses zilizobadilishwa) kwa ajili ya stack traces na `instanceof` checks.
- Kama **haswa** ambapo unaweza kupona; wacha hitilafu zisizotarajiwa zizunguke.
- Usinyamazishe hitilafu kwa siri (`catch (e) {}`). Daima log au tupa upya.