# brace-expansion

[Brace expansion](https://www.gnu.org/software/bash/manual/html_node/Brace-Expansion.html),
as known from sh/bash, in JavaScript.

[![CI](https://github.com/juliangruber/brace-expansion/actions/workflows/ci.yml/badge.svg)](https://github.com/juliangruber/brace-expansion/actions/workflows/ci.yml)
[![downloads](https://img.shields.io/npm/dm/brace-expansion.svg)](https://www.npmjs.org/package/brace-expansion)

## Example

```js
import { expand } from 'brace-expansion'

expand('file-{a,b,c}.jpg')
// => ['file-a.jpg', 'file-b.jpg', 'file-c.jpg']

expand('-v{,,}')
// => ['-v', '-v', '-v']

expand('file{0..2}.jpg')
// => ['file0.jpg', 'file1.jpg', 'file2.jpg']

expand('file-{a..c}.jpg')
// => ['file-a.jpg', 'file-b.jpg', 'file-c.jpg']

expand('file{2..0}.jpg')
// => ['file2.jpg', 'file1.jpg', 'file0.jpg']

expand('file{0..4..2}.jpg')
// => ['file0.jpg', 'file2.jpg', 'file4.jpg']

expand('file-{a..e..2}.jpg')
// => ['file-a.jpg', 'file-c.jpg', 'file-e.jpg']

expand('file{00..10..5}.jpg')
// => ['file00.jpg', 'file05.jpg', 'file10.jpg']

expand('{{A..C},{a..c}}')
// => ['A', 'B', 'C', 'a', 'b', 'c']

expand('ppp{,config,oe{,conf}}')
// => ['ppp', 'pppconfig', 'pppoe', 'pppoeconf']
```

## API

```js
import { expand } from 'brace-expansion'
```

### const expanded = expand(str, [options])

Return an array of all possible and valid expansions of `str`. If
none are found, `[str]` is returned.

The `options` object can provide a `max` value to cap the number
of expansions allowed. This is limited to `100_000` by default,
to prevent DoS attacks.

```js
const expansions = expand('{1..100}'.repeat(5), {
  max: 100,
})
// expansions.length will be 100, not 100^5
```

The `options` object can also provide a `maxLength` value to cap the
total number of characters across all expansions. This is limited to
`4_000_000` by default, to prevent memory exhaustion from inputs whose
result count stays under `max` while each result grows very long.

```js
const expansions = expand('{a,b}'.repeat(1500), {
  maxLength: 10_000,
})
```

Valid expansions are:

```js
;/^(.*,)+(.+)?$/
// {a,b,...}
```

A comma separated list of options, like `{a,b}` or `{a,{b,c}}` or `{,a,}`.

```js
;/^-?\d+\.\.-?\d+(\.\.-?\d+)?$/
// {x..y[..incr]}
```

A numeric sequence from `x` to `y` inclusive, with optional increment.
If `x` or `y` start with a leading `0`, all the numbers will be padded
to have equal length. Negative numbers and backwards iteration work too.

```js
;/^-?\d+\.\.-?\d+(\.\.-?\d+)?$/
// {x..y[..incr]}
```

An alphabetic sequence from `x` to `y` inclusive, with optional increment.
`x` and `y` must be exactly one character, and if given, `incr` must be a
number.

For compatibility reasons, the string `${` is not eligible for brace expansion.
