# .replace(old,new)

## Description

The `.replace()` method replaces occurrences of text in a string. It supports both literal string replacement and regular expression patterns.

## Parameters

* `old`: The text to replace. Can be either:
  * A literal string to match exactly
  * A regex pattern in the format "/pattern/flags"
* `new`: The text to replace matches with

## Usage

### Basic String Replacement

```javascript
text = "hello world"
result = text.replace("hello", "hi")
// returns "hi world"
```

### Regular Expression Replacement

```javascript
// Replace all occurrences (global flag)
text = "hello hello hello"
result = text.replace("/hello/g", "hi")
// returns "hi hi hi"

// Case insensitive match
text = "Hello HELLO hello"
result = text.replace("/hello/gi", "hi")
// returns "hi hi hi"
```

## Regex Flags

When using regex patterns, you can add flags after the closing slash:

* `g` - global (replace all matches)
* `i` - case insensitive
* `m` - multiline

## Examples

```javascript
// Basic replacement (first occurrence only)
"The cat and the cat".replace("cat", "dog")
// returns "The dog and the cat"

// Global replacement of all occurrences
"The cat and the cat".replace("/cat/g", "dog")
// returns "The dog and the dog"

// Case insensitive replacement
"Hello HELLO hello".replace("/hello/gi", "hi")
// returns "hi hi hi"
```