regexCharacterClassRanges

Reports character class elements that can be simplified to ranges.

✅ This rule is included in the ts stylistic presets.

Character class ranges in regular expressions are more concise than listing individual consecutive characters. When four or more consecutive characters appear in a character class, they can be combined into a range for better readability.

Examples

❌ Incorrect

const letters = /[abcd]/;

const digits = /[0123]/;

const uppercase = /[ABCD]/;

const mixedWithRange = /[a-cd]/;

✅ Correct

const letters = /[a-d]/;

const digits = /[0-3]/;

const uppercase = /[A-D]/;

// Three consecutive characters are allowed (below the threshold)
const short = /[abc]/;

// Non-consecutive characters cannot be simplified
const vowels = /[aeiou]/;

// Existing ranges are already optimal
const allLetters = /[a-z]/;

Options

This rule is not configurable.

When Not To Use It

If you prefer listing individual characters for clarity (for example, when the characters represent specific values rather than a range), you might prefer to disable this rule. Some developers find explicit character lists easier to understand when the character set represents distinct concepts.

Further Reading

• MDN: Regular expressions - Character classes
• MDN: Character class escape

Equivalents in Other Linters

• ESLint: regexp/prefer-range