2025-06-30 09:38:03 +08:00

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# @isaacs/balanced-match
A hybrid CJS/ESM TypeScript fork of
[balanced-match](http://npm.im/balanced-match).
Match balanced string pairs, like `{` and `}` or `<b>` and `</b>`. Supports regular expressions as well!
[![CI](https://github.com/juliangruber/balanced-match/actions/workflows/ci.yml/badge.svg)](https://github.com/juliangruber/balanced-match/actions/workflows/ci.yml)
[![downloads](https://img.shields.io/npm/dm/balanced-match.svg)](https://www.npmjs.org/package/balanced-match)
## Example
Get the first matching pair of braces:
```js
import { balanced } from '@isaacs/balanced-match'
console.log(balanced('{', '}', 'pre{in{nested}}post'))
console.log(balanced('{', '}', 'pre{first}between{second}post'))
console.log(balanced(/\s+\{\s+/, /\s+\}\s+/, 'pre { in{nest} } post'))
```
The matches are:
```bash
$ node example.js
{ start: 3, end: 14, pre: 'pre', body: 'in{nested}', post: 'post' }
{ start: 3,
end: 9,
pre: 'pre',
body: 'first',
post: 'between{second}post' }
{ start: 3, end: 17, pre: 'pre', body: 'in{nest}', post: 'post' }
```
## API
### const m = balanced(a, b, str)
For the first non-nested matching pair of `a` and `b` in `str`, return an
object with those keys:
- **start** the index of the first match of `a`
- **end** the index of the matching `b`
- **pre** the preamble, `a` and `b` not included
- **body** the match, `a` and `b` not included
- **post** the postscript, `a` and `b` not included
If there's no match, `undefined` will be returned.
If the `str` contains more `a` than `b` / there are unmatched pairs, the first match that was closed will be used. For example, `{{a}` will match `['{', 'a', '']` and `{a}}` will match `['', 'a', '}']`.
### const r = balanced.range(a, b, str)
For the first non-nested matching pair of `a` and `b` in `str`, return an
array with indexes: `[ <a index>, <b index> ]`.
If there's no match, `undefined` will be returned.
If the `str` contains more `a` than `b` / there are unmatched pairs, the first match that was closed will be used. For example, `{{a}` will match `[ 1, 3 ]` and `{a}}` will match `[0, 2]`.