regexEmptyCapturingGroups

Reports capturing groups that only capture empty strings.

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

Reports capturing groups in regular expressions that can only capture zero-length strings. A capturing group that never captures any text is likely a mistake or unnecessary.

Examples

Empty Capturing Group

A capturing group with no content.

❌ Incorrect

const pattern = /()/;

✅ Correct

const pattern = /(a)/;

Capturing Group with Only Assertions

Assertions match positions, not characters, so a capturing group containing only assertions captures nothing.

❌ Incorrect

const pattern = /(\b)/;

✅ Correct

const pattern = /\b/;

Zero-Length Quantifiers

A quantifier with min=0 like * or ? applied to all elements means the group can match zero characters.

❌ Incorrect

const pattern = /(a*)/;

✅ Correct

const pattern = /(a+)/;

RegExp Constructor

The rule also checks regex patterns in RegExp constructor calls.

❌ Incorrect

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

✅ Correct

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

Options

This rule is not configurable.

When Not To Use It

If you intentionally use empty capturing groups for indexing purposes or other as a stylistic choice, you might prefer to disable this rule.

Further Reading

• MDN: Capturing groups
• MDN: Assertions

Equivalents in Other Linters

• ESLint: regexp/no-empty-capturing-group