Common Regular Expressions for Validating Numbers, Characters, and Special Formats

Numeric Validation Expressions – A series of regex patterns to match simple digits ( ^[0-9]*$), fixed‑length numbers ( ^\d{n}$), numbers with optional leading zeros ( ^(0|[1-9][0-9]*)$), positive/negative integers, decimals with specific precision (e.g., ^(\-)?\d+(\.\d{1,2})?$), and monetary formats allowing commas and optional cents (e.g., ^[0-9]{1,3}(,[0-9]{3})*(\.[0-9]{1,2})?$).

Character Validation Expressions – Regexes for Chinese characters ( ^[\u4e00-\u9fa5]{0,}$), alphanumeric strings ( ^[A-Za-z0-9]+$), specific length constraints ( ^.{3,20}$), uppercase or lowercase letters only ( ^[A-Z]+$, ^[a-z]+$), and strings that may include underscores ( ^\w+$), as well as patterns that exclude certain symbols (e.g., [^%&',;=?$\x22]+).

Special‑Purpose Validation Expressions – Common patterns for email addresses ( ^\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$), domain names, URLs, Chinese mobile numbers, telephone numbers, ID numbers, passwords (including strong password requirements ^(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,10}$), date formats with leap‑year handling, IP v4/v6 addresses, subnet masks, and HTML tag extraction. Additional utilities include whitespace line removal ( \n\s*\r), comment extraction ( <!--(.*?)-->), and file extension validation.

References for further learning are provided, such as the Runoob regex tutorial and online regex testing tools.