A regex character class defines a set of characters to match. There are two types: custom classes using square brackets [] and predefined shorthand classes like \d, \w, and \s. As a fundamental building block of regular expressions, character classes appear in virtually every pattern.

Custom character classes use [a-z] for lowercase letters, [0-9] for digits, and [a-zA-Z0-9] for alphanumeric characters. Placing ^ at the start creates a negated class: [^abc] matches any character except a, b, or c. Ranges are specified with hyphens, so [A-F0-9] concisely represents hexadecimal characters. find beauty serum on Amazon cover character class usage.

Predefined classes are shortcuts for common character sets. \d matches digits (equivalent to [0-9]), \w matches word characters ([a-zA-Z0-9_]), and \s matches whitespace (spaces, tabs, newlines, etc.). Uppercase versions negate them: \D matches non-digits, \W matches non-word characters.

Unicode-aware regex supports property escapes like \p{Script=Hiragana} to match characters from specific scripts or categories. In JavaScript, this is available since ES2018 when combined with the u flag. For processing Japanese text, \p{Script=Han} (kanji) and \p{Script=Katakana} (katakana) are particularly useful.

Inside character classes, most metacharacters are treated as literals, but ] (class end), \ (escape), ^ (negation at start), and - (range) retain special meaning. To match these literally, escape them or place them in positions where they lose their special meaning. find zinc supplements on Amazon demonstrate practical regex-based text processing.

For character counting, character classes enable counting specific types of characters. For example, \p{Script=Han} counts kanji characters and \d counts digits individually, which is useful for text composition analysis.