Regular expressions (regex) are powerful tools for pattern matching and text manipulation. Whether you're validating data, searching for specific strings, or parsing complex formats, regex is essential. Let's dive into the basics!

🧩 Core Concepts

  • Literal Characters: Match exact characters (e.g., a matches the letter "a").
  • Metacharacters: Special symbols like . (any character), * (zero or more), and + (one or more).
  • Character Classes: Use [abc] to match any one of the characters inside the brackets.
  • Anchors: ^ (start of string) and $ (end of string) ensure patterns match entire text.

✅ Practical Examples

  1. Email Validation
    Pattern: ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$

    Email Format

  2. Password Rules
    Pattern: ^(?=.*[A-Z])(?=.*[a-z])(?=.*\d)[A-Za-z\d]{8,}$

    Password Rules

  3. URL Matching
    Pattern: ^(https?://)?([a-zA-Z0-9-]+\.)+[a-zA-Z]{2,}(/[^\s]*)?$

    URL Pattern

⚠️ Common Pitfalls

  • Forgetting to escape special characters (e.g., \. for a literal dot).
  • Overusing greedy quantifiers (*, +) without using ? for non-greedy behavior.
  • Misusing anchors, which can lead to partial matches.

📚 Further Reading

Check out our Regex Tutorial for advanced techniques and real-world use cases.

Regex Tutorial