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# prefer-named-capture-group

[Added in v0.9.1](https://github.com/web-infra-dev/rslint/releases/tag/v0.9.1)
## Configuration


```ts title=rslint.config.ts
import { defineConfig, js } from '@rslint/core';

export default defineConfig([
  js.configs.recommended,
  {
    rules: {
      'prefer-named-capture-group': 'error',
    },
  },
]);
```

## Rule Details

This rule enforces using named capture groups instead of numbered capture
groups in regular expressions. Named capture groups make a regular
expression's intent easier to read, and make the captured values easier to
retrieve (`match.groups.name` instead of a numbered index that shifts if the
pattern changes).

This rule checks regex literals as well as string patterns passed to the
`RegExp` constructor, including stable local aliases initialized from
`RegExp` or `globalThis`/`window`/`self`/`global`, when the pattern is
statically determinable.

Examples of **incorrect** code for this rule:

```javascript
const foo = /(ba[rz])/;
const bar = new RegExp("(ba[rz])");
const baz = RegExp("(ba[rz])");

foo.exec("bar")[1]; // Retrieve the group result.
```

Examples of **correct** code for this rule:

```javascript
const foo = /(?<id>ba[rz])/;
const bar = new RegExp("(?<id>ba[rz])");
const baz = RegExp("(?<id>ba[rz])");
const xyz = /xyz(?:zy|abc)/;

foo.exec("bar").groups.id; // Retrieve the group result.
```

## Options

This rule has no configurable options.

## Differences from ESLint

- ESLint reports some indirect constructor calls that rslint currently skips.
  This includes aliases created by destructuring, a parameter default, or a
  separate assignment, as well as an alias assigned again anywhere in the
  file.
- If a single call can resolve to the global `RegExp` through more than 128
  logical or conditional branches, rslint reports at most 128 warnings for
  each unnamed capture group.
- A pattern that uses a Unicode property added after rslint's bundled Unicode
  version may be accepted by the target runtime but not reported by this rule.
- Suggested edits can differ from ESLint: rslint omits an edit that would make
  the pattern invalid and may choose a different temporary group name to avoid
  reusing one already present in the pattern.

## When Not To Use It

If you are targeting ECMAScript 2017 or older environments, you should
disable this rule, because named capture groups are only supported in
ECMAScript 2018 and newer environments.

## Original Documentation

- [ESLint: prefer-named-capture-group](https://eslint.org/docs/latest/rules/prefer-named-capture-group)
- [Source code](https://github.com/eslint/eslint/blob/v10.8.1/lib/rules/prefer-named-capture-group.js)