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

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

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

Common Patterns

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

Email Validation

```javascript 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.