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It can **remove, add and replace elements right in the original array**.

## Syntax

```javascript
array.splice(start, deleteCount, item1, item2, ...);
```

| Parameter | What it does |
|---|---|
| `start` | The index at which changes start |
| `deleteCount` | How many elements to remove |
| `item1, item2, ...` | Elements to insert in place of the removed ones (optional) |

## 1. Removing elements

```javascript
const arr = ["a", "b", "c", "d"];
const removed = arr.splice(1, 2);

console.log(arr);     // ["a", "d"]
console.log(removed); // ["b", "c"]
```

- From position `1`, remove `2` elements.
- Returns an array of the **removed elements**.
- The original array is changed.

## 2. Adding elements

```javascript
const arr = ["a", "d"];
arr.splice(1, 0, "b", "c");

console.log(arr); // ["a", "b", "c", "d"]
```

- `deleteCount = 0` means nothing is removed.
- We add `"b"` and `"c"` at position `1`.
- Everything that came after shifts to the right.

## 3. Replacing elements

```javascript
const arr = ["a", "b", "c"];
arr.splice(1, 1, "x", "y");

console.log(arr); // ["a", "x", "y", "c"]
```

- Starting at index `1`, remove `1` element (`"b"`)
- and insert `"x"`, `"y"` in its place.
- You can think of this as **removal + insertion at the same time**.

## 4. Using negative indexes

```javascript
const arr = [1, 2, 3, 4];
arr.splice(-2, 1); // remove one element starting from the end

console.log(arr); // [1, 2, 4]
```

`-2` means "the second element from the end".

## 5. If you remove more than exists

```javascript
const arr = [1, 2];
arr.splice(1, 10);
console.log(arr); // [1]
```

The method does not throw an error, it just removes everything there is starting from position `1`.

## In short:

| What it does | Example | Result |
|---|---|---|
| Removes | `arr.splice(1, 2)` | Removes 2 elements starting at index 1 |
| Adds | `arr.splice(2, 0, "x")` | Inserts "x" at position 2 |
| Replaces | `arr.splice(1, 1, "x")` | Changes 1 element to "x" |
| Returns | `["removed elements"]` | array of removed values |
| Mutates the original array | Yes | |

## An "all at once" example

```javascript
const arr = [1, 2, 3, 4, 5];

// remove 2 elements starting at index 1 and insert new ones
const removed = arr.splice(1, 2, "a", "b", "c");

console.log(arr);     // [1, "a", "b", "c", 4, 5]
console.log(removed); // [2, 3]
```

> **Summary:**
> `splice()` is a **universal "Swiss army knife"** for arrays:
> it **removes, adds and replaces elements right in the original array**
> and returns an array of the **removed** values.

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