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
✅ Correct

const 
const pattern: RegExp
pattern = /[a-a]/;

const 
const pattern: RegExp
pattern = /[a]/;

Adjacent Range

A range that spans only two consecutive characters.

❌ Incorrect
✅ Correct

const 
const pattern: RegExp
pattern = /[a-b]/;

const 
const pattern: RegExp
pattern = /[ab]/;

RegExp Constructor

The rule also checks regex patterns in RegExp constructor calls.

❌ Incorrect
✅ Correct

const 
const pattern: RegExp
pattern = new 
var RegExp: RegExpConstructor
new (pattern: RegExp | string, flags?: string) => RegExp (+2 overloads)
RegExp("[0-1]");

const 
const pattern: RegExp
pattern = new 
var RegExp: RegExpConstructor
new (pattern: RegExp | string, flags?: string) => RegExp (+2 overloads)
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.

Equivalents in Other Linters

ESLint: regexp/no-useless-range

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