regexUnnecessaryCharacterRanges

Reports character class ranges that span only one or two characters.

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

Reports character class ranges that are unnecessary because they span only one or two characters. A range like [a-a] matches only one character and can be simplified to [a]. A range like [a-b] matches only two adjacent characters and can be written as [ab].

Examples

Identity Range

A range where the start and end are the same character.

❌ Incorrect

const pattern = /[a-a]/;

✅ Correct

const pattern = /[a]/;

Adjacent Range

A range that spans only two consecutive characters.

❌ Incorrect

const pattern = /[a-b]/;

✅ Correct

const pattern = /[ab]/;

RegExp Constructor

The rule also checks regex patterns in RegExp constructor calls.

❌ Incorrect

const pattern = new RegExp("[0-1]");

✅ Correct

const pattern = new RegExp("[01]");

Options

This rule is not configurable.

When Not To Use It

If you prefer the explicit range syntax for readability or consistency, even when it spans only one or two characters, you might prefer to disable this rule.

Further Reading

• MDN: Character classes

Equivalents in Other Linters

• ESLint: regexp/no-useless-range