JavaScript Regular Expressions

What are Regular Expressions?

Regular expressions (regex) match patterns in text. Like a search pattern.

┌─────────────────────┐
│   Text: "hello123"  │
│   Pattern: /\d+/    │
│   Match: "123"      │
└─────────────────────┘

Basic Usage

const pattern = /hello/;
const text = 'hello world';

pattern.test(text); // true
text.match(pattern); // ['hello']

Common Patterns

/\d/        // Match digit
/\w/        // Match word character
/\s/        // Match whitespace
/^start/     // Match start
/end$/       // Match end

Email Validation

const emailPattern = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
emailPattern.test('user@example.com'); // true

Key Takeaway

Regex matches text patterns. Use for validation and text processing. Powerful but complex. Essential for form validation.