# The `swap64` function in Node.js Buffer Module
The **`swap64`** function is a member function of `Buffer` class in the Node.js Buffer Module. The `swap64` function is used to swap the byte order in place of a `Buffer` instance by considering it a 64-bit (or 8 bytes) array. The syntax of the `swap64` function is as follows:
```js
buf.swap64()
```
## Parameters
`swap64` takes no parameters.

## Return value
- Returns a reference to `buf` of type `Buffer`.

## Description
The `swap64` function reverses every 8-byte group present in the buffer `buf` by treating the `buf` as a 64-bit (or 8 bytes) array.

# Example usage of the `swap64` function
The following code snippet provides an example of how to use the `swap64` function:

const b = Buffer.from([0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7]);
console.log("Buffer before swap64:")
console.log(b);

b.swap64();
console.log("Buffer after swap64:")
console.log(b);

In the example above, the first group of 4 bytes (`00`, `01`, `02`, `03`, `04`, `05`, `06`, `07`) is reversed, resulting in the order `07`, `06`, `05`, `04`, `03`, `02`, `01`, `00`.

If the number of bytes is not enough to form 8-byte groups, then `ERR_INVALID_BUFFER_SIZE` error is thrown. Below is an example:

const b = Buffer.from([0x0, 0x1, 0x2, 0x3, 0x4, 0x5]);
console.log("Buffer before swap64:")
console.log(b);

b.swap64();
console.log("Buffer after swap64:")
console.log(b);

What is swap64() in Node.js Buffer Module?

Swaps the byte order of a Buffer instance in 64-bit groups, reversing every 8-byte segment.

What is swap64() in Node.js Buffer Module?

The swap64 function in Node.js Buffer Module

Parameters

Return value

Description

Example usage of the swap64 function

The `swap64` function in Node.js Buffer Module

Example usage of the `swap64` function