eslint-plugin-regexp

Introduction

eslint-plugin-regexp is ESLint plugin for finding RegExp mistakes and RegExp style guide violations.

Features

This ESLint plugin provides linting rules relate to better ways to help you avoid problems when using RegExp.

• Find the wrong usage of regular expressions, and their hints.
• Enforces a consistent style of regular expressions.
• Find hints for writing optimized regular expressions.
• 80 plugin rules for regular expression syntax and features.

You can check on the Online DEMO.

Documentation

See documents.

Installation

npm install --save-dev eslint eslint-plugin-regexp

Requirements

• ESLint v9.38.0 and above
• Node.js v20.19.0, v22.13.0, v24 and above

Usage

Add regexp to the plugins section of your eslint.config.js configuration file (you can omit the eslint-plugin- prefix) and either use one of the two configurations available (recommended or all) or configure the rules you want:

The recommended configuration

The plugin.configs.recommended config enables a subset of the rules that should be most useful to most users. See lib/configs/rules/recommended.ts for more details.

// eslint.config.js
import regexpPlugin from "eslint-plugin-regexp"

export default [
    regexpPlugin.configs.recommended,
];

Advanced Configuration

Override/add specific rules configurations. See also: http://eslint.org/docs/user-guide/configuring.

// eslint.config.js
import regexpPlugin from "eslint-plugin-regexp"

export default [
    {
        plugins: { regexp: regexpPlugin },
        rules: {
            // Override/add rules settings here, such as:
            "regexp/rule-name": "error"
        }
    }
];

Using the all configuration

The plugin.configs.all config enables all rules. It's meant for testing, not for production use because it changes with every minor and major version of the plugin. Use it at your own risk. See lib/configs/rules/all.ts for more details.

Rules

Configurations enabled in.
Configurations set to warn in.
Set in the flat/recommended configuration.
Set in the recommended configuration.
Automatically fixable by the --fix CLI option.
Manually fixable by editor suggestions.

Possible Errors

Name	Description
no-contradiction-with-assertion	disallow elements that contradict assertions
no-control-character	disallow control characters
no-dupe-disjunctions	disallow duplicate disjunctions
no-empty-alternative	disallow alternatives without elements
no-empty-capturing-group	disallow capturing group that captures empty.
no-empty-character-class	disallow character classes that match no characters
no-empty-group	disallow empty group
no-empty-lookarounds-assertion	disallow empty lookahead assertion or empty lookbehind assertion
no-escape-backspace	disallow escape backspace ([\b])
no-invalid-regexp	disallow invalid regular expression strings in RegExp constructors
no-lazy-ends	disallow lazy quantifiers at the end of an expression
no-misleading-capturing-group	disallow capturing groups that do not behave as one would expect
no-misleading-unicode-character	disallow multi-code-point characters in character classes and quantifiers
no-missing-g-flag	disallow missing g flag in patterns used in String#matchAll and String#replaceAll
no-optional-assertion	disallow optional assertions
no-potentially-useless-backreference	disallow backreferences that reference a group that might not be matched
no-super-linear-backtracking	disallow exponential and polynomial backtracking
no-super-linear-move	disallow quantifiers that cause quadratic moves
no-useless-assertions	disallow assertions that are known to always accept (or reject)
no-useless-backreference	disallow useless backreferences in regular expressions
no-useless-dollar-replacements	disallow useless $ replacements in replacement string
strict	disallow not strictly valid regular expressions

Best Practices

Name	Description
confusing-quantifier	disallow confusing quantifiers
control-character-escape	enforce consistent escaping of control characters
negation	enforce use of escapes on negation
no-dupe-characters-character-class	disallow duplicate characters in the RegExp character class
no-empty-string-literal	disallow empty string literals in character classes
no-extra-lookaround-assertions	disallow unnecessary nested lookaround assertions
no-invisible-character	disallow invisible raw character
no-legacy-features	disallow legacy RegExp features
no-non-standard-flag	disallow non-standard flags
no-obscure-range	disallow obscure character ranges
no-octal	disallow octal escape sequence
no-standalone-backslash	disallow standalone backslashes (\)
no-trivially-nested-assertion	disallow trivially nested assertions
no-trivially-nested-quantifier	disallow nested quantifiers that can be rewritten as one quantifier
no-unused-capturing-group	disallow unused capturing group
no-useless-character-class	disallow character class with one character
no-useless-flag	disallow unnecessary regex flags
no-useless-lazy	disallow unnecessarily non-greedy quantifiers
no-useless-quantifier	disallow quantifiers that can be removed
no-useless-range	disallow unnecessary character ranges
no-useless-set-operand	disallow unnecessary elements in expression character classes
no-useless-string-literal	disallow string disjunction of single characters in \q{...}
no-useless-two-nums-quantifier	disallow unnecessary {n,m} quantifier
no-zero-quantifier	disallow quantifiers with a maximum of zero
optimal-lookaround-quantifier	disallow the alternatives of lookarounds that end with a non-constant quantifier
optimal-quantifier-concatenation	require optimal quantifiers for concatenated quantifiers
prefer-escape-replacement-dollar-char	enforces escape of replacement $ character ($).
prefer-predefined-assertion	prefer predefined assertion over equivalent lookarounds
prefer-quantifier	enforce using quantifier
prefer-range	enforce using character class range
prefer-regexp-exec	enforce that RegExp#exec is used instead of String#match if no global flag is provided
prefer-regexp-test	enforce that RegExp#test is used instead of String#match and RegExp#exec
prefer-set-operation	prefer character class set operations instead of lookarounds
require-unicode-regexp	enforce the use of the u flag
require-unicode-sets-regexp	enforce the use of the v flag
simplify-set-operations	require simplify set operations
sort-alternatives	sort alternatives if order doesn't matter
use-ignore-case	use the i flag if it simplifies the pattern

Stylistic Issues

Name	Description
grapheme-string-literal	enforce single grapheme in string literal
hexadecimal-escape	enforce consistent usage of hexadecimal escape
letter-case	enforce into your favorite case
match-any	enforce match any character style
no-useless-escape	disallow unnecessary escape characters in RegExp
no-useless-non-capturing-group	disallow unnecessary non-capturing group
prefer-character-class	enforce using character class
prefer-d	enforce using \d
prefer-lookaround	prefer lookarounds over capturing group that do not replace
prefer-named-backreference	enforce using named backreferences
prefer-named-capture-group	enforce using named capture groups
prefer-named-replacement	enforce using named replacement
prefer-plus-quantifier	enforce using + quantifier
prefer-question-quantifier	enforce using ? quantifier
prefer-result-array-groups	enforce using result array groups
prefer-star-quantifier	enforce using * quantifier
prefer-unicode-codepoint-escapes	enforce use of unicode codepoint escapes
prefer-w	enforce using \w
sort-character-class-elements	enforces elements order in character class
sort-flags	require regex flags to be sorted
unicode-escape	enforce consistent usage of unicode escape or unicode codepoint escape
unicode-property	enforce consistent naming of unicode properties

Removed

• These rules have been removed in a previous major release, after they have been deprecated for a while.

Rule ID	Replaced by	Removed in version
no-assertion-capturing-group	regexp/no-empty-capturing-group	v2.0.0
no-useless-exactly-quantifier	regexp/no-useless-quantifier, regexp/no-zero-quantifier	v2.0.0
no-useless-non-greedy	regexp/no-useless-lazy	v2.0.0
order-in-character-class	regexp/sort-character-class-elements	v2.0.0
prefer-t	regexp/control-character-escape	v2.0.0

Settings

See Settings.

Semantic Versioning Policy

eslint-plugin-regexp follows Semantic Versioning and ESLint's Semantic Versioning Policy.

Contributing

Welcome contributing!

Please use GitHub's Issues/PRs.

See CONTRIBUTING.md.

Development Tools

• npm test runs tests and measures coverage.
• npm run update runs in order to update readme and recommended configuration.
• npm run new [new rule name] runs to create the files needed for the new rule.
• npm run docs:watch starts the website locally.

License

See the LICENSE file for license rights and limitations (MIT).