regexMisleadingQuantifiers

Reports quantifiers whose minimum implies they must match but whose element can match empty.

✅ This rule is included in the ts logical presets.

Reports quantifiers whose minimum implies they must match but whose element can match empty. These quantifiers are misleading because they suggest a minimum number of matches, but the quantified element can match the empty string, making the effective minimum 0.

Examples

Optional Element with Fixed Repetition

❌ Incorrect

const pattern = /(a?){5}/;

✅ Correct

const pattern = /(a?){0,5}/;

The {5} suggests exactly 5 matches are required, but since a? can match empty, the pattern can match the empty string.

Alternation with Optional Elements

❌ Incorrect

const pattern = /(?:a?b*|c+){4}/;

✅ Correct

const pattern = /(?:a?b*|c+){0,4}/;

The {4} suggests at least 4 matches, but the a?b* alternative can match empty.

Plus Quantifier on Empty-Matchable Group

❌ Incorrect

const pattern = /(a?)+/;

✅ Correct

const pattern = /(a?)*/;

The + suggests at least 1 match is required, but a? can match empty.

Options

This rule is not configurable.

When Not To Use It

If you use misleading quantifiers intentionally for backtracking behavior, or if you use quantifiers to control iteration count rather than match content, you might want to disable this rule.

Further Reading

• MDN: Quantifier
• MDN: Groups and backreferences

Equivalents in Other Linters

• ESLint: regexp/confusing-quantifier