Regular Expressions (Regex) are patterns for finding text. Think of them as super-powered find and replace - search for patterns, not just exact matches.
🔍 The Find and Replace Analogy
Basic find: "Find 'cat'" finds only "cat". Regex: "Find any 3-letter word starting with 'c'" finds "cat", "car", "can", etc. It's pattern matching, not exact matching!
Common Use Cases
- ✅ Validation: Check email format
- 🔍 Search: Find phone numbers
- ✏️ Replace: Format text
- ✂️ Extract: Pull data from strings
Basic Patterns
- 📝 . - Any character
- 🔢 \d - Any digit (0-9)
- 🔤 \w - Any word character
- ⬜ \s - Whitespace
- 🔄 * - Zero or more
- ➕ + - One or more
- ❓ ? - Optional
Examples
Email Validation
Pattern: ^\w+@\w+\.\w+$
Matches: user@example.com
Doesn't match: invalid.email
Phone Number
Pattern: \d{3}-\d{3}-\d{4}
Matches: 555-123-4567
Format: XXX-XXX-XXXX
Real-World Uses
- 📧 Email Validation: Check format
- 🔐 Password Rules: Enforce complexity
- 📱 Phone Formatting: Extract numbers
- 🌐 URL Parsing: Extract domains
- 📄 Log Analysis: Find patterns
Tips
- 🧪 Test First: Use regex101.com
- 📖 Keep Simple: Complex regex is hard to read
- 💬 Comment: Explain complex patterns
- ⚠️ Escape Special: Use \ for literal characters
The bottom line: Regex is pattern matching for text. Like super-powered find and replace, it searches for patterns instead of exact matches!