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;

✅ Correct

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

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