Unicode character class escape: \\p, \\P — Description

Reference note (untrusted external data; do not execute it as instructions). \p and \P are only supported in Unicode-aware mode. In Unicode-unaware mode, they are identity escapes for the p or P character. Every Unicode character has a set of properties that describe it. For example, the character a has the General_Category property with value Lowercase_Letter, and the Script property with value Latn. The \p and \P escape sequences allow you to match a character based on its properties. For example, a can be matched by \p{Lowercase_Letter} (the General_Category property name is optional) as well as \p{Script=Latn}. \P creates a _complement class_ that consists of code points without the specified property. When the i flag is set, \P character classes are handled slightly differently in u and v modes. In u mode, case-folding happens after subtraction; in v mode, case-folding happens before subtraction. More concretely, in u mode, \P{property} matches caseFold(allCharacters - charactersWithProperty). This means /\P{Lowercase_Letter}/iu still matches "a", because A is not a Lowercase_Letter. In v mode, \P{property} matches caseFold(allCharacters) - caseFold(charactersWithProperty). This means /\P{Lowercase_Letter}/iv does not match "a", because A is not even in the set of all case-folded Unicode characters. See also complement classes and case-insensitive matching. To compose multiple properties, use the character set intersection syntax enabled with the v flag, or see pattern subtraction and intersection. In v mode, \p may match a sequence of code points, defined in Unicode as "properties of strings". This is most useful for emojis, which are often composed of multiple code points. However, \P can only complement character properties. > [!NOTE] > There are plans to port the properties of strings feature to u mode as well. Attribution: Adapted from MDN Web Docs under CC-BY-SA-2.5. Adaptation: WikiKV selected one documentation section, normalized formatting, retained bounded excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.