regexEmptyGroups

Reports empty groups in regular expressions.

✅ This rule is included in the ts logical and logicalStrict presets.

Reports empty capturing and non-capturing groups in regular expressions. Empty groups like () or (?:) match the empty string and have no meaningful effect on the regex pattern. This rule reports those empty groups.

Examples

Empty Capturing Group

❌ Incorrect

const pattern = /()/;

✅ Correct

const pattern = /(a)/;

Empty Non-Capturing Group

❌ Incorrect

const pattern = /(?:)/;

✅ Correct

const pattern = /(?:a)/;

Empty Group with Empty Alternatives

❌ Incorrect

const pattern = /(|)/;

✅ Correct

const pattern = /(a|)/;

RegExp Constructor

❌ Incorrect

const pattern = new RegExp("()");

✅ Correct

const pattern = new RegExp("(a)");

Options

This rule is not configurable.

When Not To Use It

If you are intentionally using empty groups for some specific purpose in generated or legacy code, such as for stylistic separations, you might prefer to disable this rule. You might consider using Flint disable comments and/or configuration file disables for those specific situations instead of completely disabling this rule.

Further Reading

• MDN: Groups and backreferences
• MDN: Non-capturing group

Equivalents in Other Linters

• ESLint: regexp/no-empty-group