#no-empty-character-class

#Configuration

import { defineConfig, js } from '@rslint/core';

export default defineConfig([
  js.configs.recommended,
  {
    rules: {
      'no-empty-character-class': 'error',
    },
  },
]);

#Rule Details

Disallows empty character classes [] in regular expression literals. An empty character class in a regular expression does not match anything and is almost certainly a mistake. Note that [^] (a negated empty class) is allowed since it matches any character.

With the ES2024 v flag (unicodeSets), character classes can be nested. This rule also detects empty classes inside nested structures such as set subtraction (--) and intersection (&&).

This rule does not check new RegExp() constructor calls — only regex literals.

Examples of incorrect code for this rule:

var foo = /^abc[]/;
var foo = /foo[]bar/;
var foo = /[]]/;
// v-flag (ES2024)
var foo = /[[]]/v;
var foo = /[a--[]]/v;
var foo = /[a&&[]]/v;

Examples of correct code for this rule:

var foo = /^abc[a-zA-Z]/;
var foo = /[^]/;
var foo = /[\\[]/;
var foo = /\\[]/;
// v-flag (ES2024)
var foo = /[[^]]/v;
var foo = /[a--b]/v;
var foo = /[[a][b]]/v;

#Original Documentation

• ESLint no-empty-character-class