Regular Expressions: Practical Guide for Developers
Regular expressions are powerful pattern-matching tools used in every programming language. They can seem intimidating, but learning the basics covers most real-world use cases.
Essential Patterns
Character Classes
\d matches any digit (0-9). \w matches word characters (letters, digits, underscore). \s matches whitespace. The uppercase versions (\D, \W, \S) match the opposite.
Quantifiers
- matches zero or more. + matches one or more. ? matches zero or one. {n} matches exactly n times. {n,m} matches between n and m times.
Anchors
^ matches the start of a string. $ matches the end. \b matches a word boundary.
Common Patterns
Email validation: a basic pattern checks for text@text.text format. Phone numbers: match digits with optional separators. URLs: match protocol, domain, and optional path. Our Regex Tester lets you experiment with patterns in real time.
Capture Groups
Parentheses create capture groups that extract parts of a match. Named groups using (?
Performance Tips
Avoid catastrophic backtracking by being specific with quantifiers. Use possessive quantifiers or atomic groups when available. Test complex patterns with various inputs to catch performance issues early.
> Try our dev tools