regexEmptyLazyQuantifiers

Reports lazy quantifiers at the end of regular expressions.

✅ This rule is included in the ts logical presets.

Reports lazy quantifiers at the end of regular expressions that will never match more than their minimum. Lazy quantifiers like *?, +?, or {n,m}? at the end of a pattern are useless because there is nothing after them to require a larger match.

Examples

Zero Minimum (Will Match Empty String)

❌ Incorrect

const pattern = /a*?/;

✅ Correct

const pattern = /a*?b/;

One Minimum (Will Match Exactly Once)

❌ Incorrect

const pattern = /a+?/;

✅ Correct

const pattern = /a+?b/;

Range Minimum (Will Match Minimum Times)

❌ Incorrect

const pattern = /a{3,7}?/;

✅ Correct

const pattern = /a{3,7}?b/;

Inside Groups

❌ Incorrect

const pattern = /(?:a|bc+?)/;

✅ Correct

const pattern = /(?:a|bc+?)d/;

Options

This rule is not configurable.

When Not To Use It

If you tend to use patterns as a partials (e.g., to combine with other patterns via string concatenation), you might need to disable this rule.

Further Reading

• MDN: Quantifier
• MDN: Regular expressions

Equivalents in Other Linters

• ESLint: regexp/no-lazy-ends