The "extends": "eslint:recommended" property in a configuration file enables this rule.
Unicode includes the characters which are made with multiple code points. RegExp character class syntax (/[abc]/) cannot handle characters which are made by multiple code points as a character; those characters will be dissolved to each code point. For example, ❇️ is made by ❇ (U+2747) and VARIATION SELECTOR-16 (U+FE0F). If this character is in RegExp character class, it will match to either ❇ (U+2747) or VARIATION SELECTOR-16 (U+FE0F) rather than ❇️.
This rule reports the regular expressions which include multiple code point characters in character class syntax. This rule considers the following characters as multiple code point characters.
A character with combining characters:
The combining characters are characters which belong to one of Mc, Me, and Mn Unicode general categories.
/^[Á]$/u.test("Á") //→ false
/^[❇️]$/u.test("❇️") //→ false
A character with Emoji modifiers:
/^[👶🏻]$/u.test("👶🏻") //→ false
/^[👶🏽]$/u.test("👶🏽") //→ false
A pair of regional indicator symbols:
/^[🇯🇵]$/u.test("🇯🇵") //→ false
Characters that ZWJ joins:
/^[👨👩👦]$/u.test("👨👩👦") //→ false
A surrogate pair without Unicode flag:
/^[👍]$/.test("👍") //→ false
// Surrogate pair is OK if with u flag.
/^[👍]$/u.test("👍") //→ true
This rule reports the regular expressions which include multiple code point characters in character class syntax.
Examples of incorrect code for this rule:
/*eslint no-misleading-character-class: error */
/^[Á]$/u
/^[❇️]$/u
/^[👶🏻]$/u
/^[🇯🇵]$/u
/^[👨👩👦]$/u
/^[👍]$/
Examples of correct code for this rule:
/*eslint no-misleading-character-class: error */
/^[abc]$/
/^[👍]$/u
You can turn this rule off if you don't want to check RegExp character class syntax for multiple code point characters.
This rule was introduced in ESLint 5.3.0.
© JS Foundation and other contributors
Licensed under the MIT License.
https://eslint.org/docs/rules/no-misleading-character-class