Regular expressions

Regular-expression rules from eslint-plugin-regexp. These rules check the structure of regex literals, emptiness, uselessness, flag ordering, shorthand classes, Unicode support. Some rules duplicate (and supersede) the regex-related rules in Core; both ids exist so projects can keep the legacy ESLint names alongside the regexp-plugin variants. Dynamic RegExp("...") constructor strings are deferred until the lint engine has a shared literal-value helper.

Source: eslint-plugin-regexp (MIT).

• regexp/no-control-character: Reject ASCII control characters in regex literals.
• regexp/no-dupe-characters-character-class: Reject duplicate literal characters inside simple regex character classes (/[aa]/).
• regexp/no-empty-alternative: Reject empty alternatives in a disjunction (/a||b/), which silently match the empty string.
• regexp/no-empty-capturing-group: Reject empty capturing groups such as /()/.
• regexp/no-empty-character-class: Reject empty regex character classes ([]).
• regexp/no-empty-group: Reject empty non-capturing groups such as /(?:)/.
• regexp/no-empty-lookarounds-assertion: Reject empty lookaround assertions such as /(?=)/ or /(?!)/.
• regexp/no-misleading-unicode-character: Reject misleading Unicode characters in regex classes.
• regexp/no-useless-character-class: Reject single-character character classes such as /[x]/, /x/ is equivalent.
• regexp/no-useless-escape: Reject unnecessary escapes inside regex literals.
• regexp/no-useless-flag: Reject regex flags that the literal does not exercise, i on a pattern without case-variable characters, m without ^/$, s without ., and similar dead flags on g/y.
• regexp/no-useless-quantifier: Reject quantifiers that do not change the match, constant-one counts (/a{1}/), ? on patterns already matching the empty string, and quantifiers on non-consuming atoms.
• regexp/no-useless-two-nums-quantifier: Reject equal min/max quantifiers (/a{2,2}/) in favor of /a{2}/.
• regexp/no-zero-quantifier: Reject zero-repeat quantifiers (/a{0}/, /a{0,0}/). The atom never matches, so the quantifier is either dead code or a typo for {1,…}.
• regexp/prefer-d: Prefer \d over [0-9] in regex literals.
• regexp/prefer-plus-quantifier: Prefer + over {1,} in regex literals.
• regexp/prefer-question-quantifier: Prefer ? over {0,1} in regex literals.
• regexp/prefer-star-quantifier: Prefer * over {0,} in regex literals.
• regexp/prefer-w: Prefer \w over [A-Za-z0-9_] in regex literals.
• regexp/require-unicode-regexp: Require regex literals to use the u or v flag, so Unicode-property escapes and surrogate-pair handling stay predictable.
• regexp/require-unicode-sets-regexp: Require regex literals to use the v flag specifically, the stricter Unicode-sets mode that enables set notation, string properties, and stricter escape rules on top of u.
• regexp/sort-flags: Require regex flags to appear in canonical alphabetical order (dgimsuvy).