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regexEmptyStringLiterals

Reports empty string literals in character classes.

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

Reports empty string literals (\q{}) in character classes when using the v (unicodeSets) flag. An empty string literal in a character class always matches the empty string, which is usually a mistake.

Examples

Section titled “Examples”

Empty String Literal

Section titled “Empty String Literal”

A \q{} with no content matches the empty string.

const 
const pattern: RegExp
pattern = /[\q{}]/v;
Error ts(1501)  ― This regular expression flag is only available when targeting 'es2024' or later.

Empty String Literal with Other Elements

Section titled “Empty String Literal with Other Elements”

Even with other elements in the character class, an empty \q{} is reported.

const 
const pattern: RegExp
pattern = /[a\q{}]/v;
Error ts(1501)  ― This regular expression flag is only available when targeting 'es2024' or later.

RegExp Constructor

Section titled “RegExp Constructor”

The rule also checks regex patterns in RegExp constructor calls.

const 
const pattern: RegExp
pattern = new 
var RegExp: RegExpConstructor
new (pattern: RegExp | string, flags?: string) => RegExp (+2 overloads)
RegExp("[\\q{}]", "v");

Non-Empty Alternatives Are Valid

Section titled “Non-Empty Alternatives Are Valid”

If the string literal has at least one non-empty alternative, it is valid.

const 
const pattern: RegExp
pattern = /[\q{a|}]/v;
Error ts(1501)  ― This regular expression flag is only available when targeting 'es2024' or later.

Options

Section titled “Options”

This rule is not configurable.

When Not To Use It

Section titled “When Not To Use It”

If you intentionally use empty string literals in character classes to match empty strings and prefer this style over using quantifiers, you might prefer to disable this rule.

Further Reading

Section titled “Further Reading”

Equivalents in Other Linters

Section titled “Equivalents in Other Linters”
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