Dbqb_Study/吴光慧学习笔记/11.1/study/node_modules/buffer-from/readme.md

# Buffer From

A [ponyfill](https://ponyfill.com) for `Buffer.from`, uses native implementation if available.

## Installation

```sh
npm install --save buffer-from
```

## Usage

```js
const bufferFrom = require('buffer-from')

console.log(bufferFrom([1, 2, 3, 4]))
//=> <Buffer 01 02 03 04>

const arr = new Uint8Array([1, 2, 3, 4])
console.log(bufferFrom(arr.buffer, 1, 2))
//=> <Buffer 02 03>

console.log(bufferFrom('test', 'utf8'))
//=> <Buffer 74 65 73 74>

const buf = bufferFrom('test')
console.log(bufferFrom(buf))
//=> <Buffer 74 65 73 74>
```

## API

### bufferFrom(array)

- `array` &lt;Array&gt;

Allocates a new `Buffer` using an `array` of octets.

### bufferFrom(arrayBuffer[, byteOffset[, length]])

- `arrayBuffer` &lt;ArrayBuffer&gt; The `.buffer` property of a TypedArray or ArrayBuffer
- `byteOffset` &lt;Integer&gt; Where to start copying from `arrayBuffer`. **Default:** `0`
- `length` &lt;Integer&gt; How many bytes to copy from `arrayBuffer`. **Default:** `arrayBuffer.length - byteOffset`

When passed a reference to the `.buffer` property of a TypedArray instance, the
newly created `Buffer` will share the same allocated memory as the TypedArray.

The optional `byteOffset` and `length` arguments specify a memory range within
the `arrayBuffer` that will be shared by the `Buffer`.

### bufferFrom(buffer)

- `buffer` &lt;Buffer&gt; An existing `Buffer` to copy data from

Copies the passed `buffer` data onto a new `Buffer` instance.

### bufferFrom(string[, encoding])

- `string` &lt;String&gt; A string to encode.
- `encoding` &lt;String&gt; The encoding of `string`. **Default:** `'utf8'`

Creates a new `Buffer` containing the given JavaScript string `string`. If
provided, the `encoding` parameter identifies the character encoding of
`string`.

## See also

- [buffer-alloc](https://github.com/LinusU/buffer-alloc) A ponyfill for `Buffer.alloc`
- [buffer-alloc-unsafe](https://github.com/LinusU/buffer-alloc-unsafe) A ponyfill for `Buffer.allocUnsafe`