regexUnicodeEscapes

Enforces consistent Unicode escape style in regex patterns by preferring codepoint escapes.

✅ This rule is included in the ts preset.

Enforces consistent Unicode escape style in regex patterns by preferring \u{XXXX} (codepoint escape) over \uXXXX (4-digit Unicode escape) when the u or v flag is present.

The \u{...} format is more flexible, readable, and consistent with the modern Unicode handling in JavaScript.

Examples

Basic Unicode Escape

❌ Incorrect

const pattern = /\u0041/u;

✅ Correct

const pattern = /\u{0041}/u;

Character Class

❌ Incorrect

const pattern = /[\u0041\u0042]/u;

✅ Correct

const pattern = /[\u{0041}\u{0042}]/u;

Character Range

❌ Incorrect

const pattern = /[\u0041-\u005A]/u;

✅ Correct

const pattern = /[\u{0041}-\u{005A}]/u;

With v Flag

❌ Incorrect

const pattern = /\u0041/v;
Error ts(1501)  ― This regular expression flag is only available when targeting 'es2024' or later.

✅ Correct

const pattern = /\u{0041}/v;
Error ts(1501)  ― This regular expression flag is only available when targeting 'es2024' or later.

Options

This rule is not configurable.

When Not To Use It

If you need to support environments that do not have the u or v flag, or if you intentionally use 4-digit Unicode escapes as a stylistic preference, you might want to disable this rule. This rule is not enabled by default in Flint because the preference for \u{...} over \uXXXX is more opinionated than what most projects prefer.

Further Reading

• MDN: Unicode character class escape

Equivalents in Other Linters

• ESLint: regexp/unicode-escape