Regex Patterns

Practical regular expression cookbook. Patterns for validation, parsing, extraction, and refactoring across JavaScript, Python, Go, and command-line tools.

When to Use

• Validating user input (email, URL, IP, phone, dates)
• Parsing log lines or structured text
• Extracting data from strings (IDs, numbers, tokens)
• Search-and-replace in code (rename variables, update imports)
• Filtering lines in files or command output
• Debugging regexes that don't match as expected

Quick Reference

Metacharacters