如何線上測試正則表達式

What are Regular Expressions?

Regular expressions (regex) are patterns used to match character combinations in strings. They're essential for:

Data Validation: Check email, phone, password formats

Text Search: Find specific patterns in large documents

Data Extraction: Pull information from unstructured text

Text Replacement: Find and replace with complex patterns

Common Regex Patterns

| Pattern | Description | Example |
|---------|-------------|---------|
| ^\d+$ | Numbers only | 12345 |
| ^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$ | Email address | user@example.com |
| ^https?:\/\/.+ | URL | https://example.com |
| \b\d{4}-\d{2}-\d{2}\b | Date (YYYY-MM-DD) | 2024-03-15 |

How to Use the Regex Tester

Step 1: Enter Pattern

Go to the Regex Tester and type your regular expression pattern.

Step 2: Enter Test Text

Paste the text you want to test against the pattern.

Step 3: View Matches

Highlighting: Matched text is highlighted in real-time

Groups: Captured groups are shown separately

Replace: Test find-and-replace operations

Tips for Writing Regex

Start Simple: Build complex patterns step by step

Test Edge Cases: Try empty strings, special characters

Use Online Resources: regex101.com for detailed explanations

Escape Special Characters: Use \ before . * + ? ^ $ ( ) [ ] { } | \

Related Tools

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Text Diff - Compare before/after replacement

Case Converter - Transform matched text

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Convert Text Case

Use Text Converter.Md