regex-tester

Regex Tester

Test regular expressions with syntax validation, match testing, group extraction, and replacement.

Features

• Validate: Check regex syntax validity
• Test: Match patterns against text
• Groups: Extract capture groups
• Replace: Find and replace with regex
• Explain: Get human-readable pattern explanation
• Flags: Support for common regex flags (global, case-insensitive, multiline, dotall)

Usage

# Test pattern matching
./scripts/regex.js --pattern "hello.*world" --text "hello there world"

Extract groups

./scripts/regex.js --pattern "(\d{3})-(\d{3})-(\d{4})" --text "555-123-4567" --groups

Replace text

./scripts/regex.js --pattern "\b(\w+)\b" --text "hello world" --replace "[$1]" --global

Validate regex syntax (no text needed)

./scripts/regex.js --pattern "[a-z+" --validate

Explain pattern

./scripts/regex.js --pattern "^(\d+).(\d+).(\d+)$" --explain

With flags

./scripts/regex.js --pattern "HELLO" --text "hello" --flags "i" # case-insensitive

## Flags

| Flag | Description |
|------|-------------|
| `g` | Global (find all matches) |
| `i` | Case-insensitive |
| `m` | Multiline (^ and $ match start/end of lines) |
| `s` | Dotall (dot matches newlines) |

## Examples

| Task | Command |
|------|---------|
| Email validation | `./scripts/regex.js --pattern "^[\w.-]+@[\w.-]+\.\w+$" --text "test@example.com"` |
| Phone extraction | `./scripts/regex.js --pattern "\d{3}-\d{3}-\d{4}" --text "Call 555-123-4567" --global` |
| URL matching | `./scripts/regex.js --pattern "https?://[^\s]+" --text "Visit https://example.com"` |
| Date parsing | `./scripts/regex.js --pattern "(\d{4})-(\d{2})-(\d{2})" --text "2024-03-15" --groups` |
| Code search | `./scripts/regex.js --pattern "function\s+(\w+)" --text "function hello() {}" --flags "g"` |

## Output Format

Valid match:
```json
{
  "valid": true,
  "matches": 2,
  "results": [
    { "match": "hello world", "index": 0, "groups": [] },
    { "match": "hello universe", "index": 12, "groups": [] }
  ]
}

No match:

{
  "valid": true,
  "matches": 0,
  "message": "No matches found"
}

Invalid pattern:

{
  "valid": false,
  "error": "Unterminated character class",
  "position": 5
}

Pattern Reference

• . - Any character (except newline)
• \d - Digit (0-9)
• \w - Word character (letters, digits, underscore)
• \s - Whitespace
• [] - Character class
• [^] - Negated character class
• * - Zero or more
• + - One or more
• ? - Zero or one
• ^ - Start of string
• $ - End of string
• () - Capture group