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## 1. The modern and reliable approach → `Array.isArray()`

```javascript
Array.isArray(value);
```

> This is the **standard ES5 method** specifically created for this check.
> It returns `true` if the value is an array, and `false` in all other cases.

### Examples for `Array.isArray()`

```javascript
Array.isArray([1, 2, 3]);     // true
Array.isArray([]);             // true
Array.isArray('text');         // false
Array.isArray({ 0: 'a', 1: 'b', length: 2 }); // false
Array.isArray(null);           // false
```

It works correctly even across different contexts (for example, iframe, window, and so on).
This makes it the **only 100% reliable approach**.

---

## 2. The old approach → `instanceof Array`

```javascript
value instanceof Array
```

### Example:

```javascript
console.log([1, 2, 3] instanceof Array); // true
console.log({} instanceof Array);        // false
```

> Drawback:
> if the array was created in **a different window or iframe**, the check returns `false`,
> because it has a different `Array` constructor.

```javascript
// example (pseudocode)
iframe.contentWindow.Array !== window.Array;
```

---

## 3. An alternative (manual) → checking via `Object.prototype.toString`

```javascript
Object.prototype.toString.call(value) === '[object Array]'
```

### Example:

```javascript
console.log(Object.prototype.toString.call([1, 2, 3])); // "[object Array]"
console.log(Object.prototype.toString.call({}));        // "[object Object]"
```

> Works correctly, but looks cumbersome:
> nowadays it is almost always replaced with `Array.isArray()`.

---

## Comparing all the approaches

| Method | Returns | Pros | Cons |
|---|---|---|---|
| `Array.isArray()` | `true/false` | Modern, reliable | None |
| `instanceof Array` | `true/false` | Clear syntax | Does not work across different contexts |
| `Object.prototype.toString.call()` | `"[object Array]"` | Always works | Verbose to write |

---

## Examples of checking different values

```javascript
console.log(Array.isArray([1, 2, 3]));      // true
console.log(Array.isArray('hello'));        // false
console.log(Array.isArray({ length: 0 }));  // false
console.log(Array.isArray(new Array()));    // true
console.log(Array.isArray(null));           // false
```

---

## In short

> Use `Array.isArray(value)`:
> it is the **most reliable and readable** way to check whether a value is an array.

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