Menene bambanci tsakanin var, let da const?

Question

IT Interview Practice · Accepted Answer

Suna bambanta ta hanyoyi uku: **scope**, **halin inyatacciyar** da **sake sanya**.

```js
function demo() {
  if (true) {
    var a = 1;    // function-scoped — leaks out of the if-block
    let b = 2;    // block-scoped — only exists inside { }
    const c = 3;  // block-scoped, can't be reassigned
  }
  console.log(a); // 1  (var escaped the block)
  console.log(b); // ReferenceError (let stayed in the block)
}
```

## Manyan bambance

- **`var`** shine **function-scoped**, hoisted kuma aka initialize zuwa `undefined`, kuma ana iya sake bayyana shi. Wannan yana haifar da abin mamaki - gba shi.
- **`let`** shine **block-scoped** (`{ }`), kuma ana iya sake bayyana shi, kuma yana zaune a cikin *temporal dead zone* har zuwa layin sake bayyanarsa (idan ka bugi shi da wuri, jiya aka sanya errar).
- **`const`** shine block-scoped kuma **ba za a iya sake bayyana shi ba** — amma lura cewa binding yana daidai, *ba kuma ba kimar:

```js
const user = { name: "Ann" };
user.name = "Bob"; // ✅ allowed — mutating the object, not reassigning
user = {};          // ❌ TypeError — can't rebind `user`
```

## Tsarin jari

Fara da **`const`**; juyawa zuwa **`let`** kawai lokacin da ka bugi sake sanya; **kada ka yi amfani da `var`** a cikin sabon code. Wannan yana bayyana intention ("wannan ba zai canja ba") kuma yana guje jujjuyin scope da abubuwan hanci hoisting da `var` ke kawo da su.

Manyan bambance

Tsarin jari

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