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正規表現（RegEx）テスター・リアルタイムパターン検証
正規表現（RegEx）テスター・リアルタイムパターン検証
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コアアーキテクチャ & 計算式
RegEx Pattern + Search Modifiers (g, i, m) ➔ Array of Matched Substrings
The pattern dictates the exact character sequence, while modifiers alter the engine's behavior (e.g., 'i' for case insensitivity, 'g' for global multiline searching).
ベストプラクティスとガイドライン
- Always Anchor Your Patterns: When validating complete strings (like an email address), always use the caret ^ at the beginning and the dollar sign $ at the end to prevent partial substring matches.
- Beware of Catastrophic Backtracking: Poorly optimized nested quantifiers (like `(a+)+`) can cause the regex engine to freeze the entire browser thread when evaluating long failing strings.
- Use Lazy Quantifiers for HTML: By default, the asterisk * is greedy and matches as much text as possible. Append a question mark `*?` to make it lazy, which is critical when extracting data between HTML tags.
よくある質問 (FAQ)
Why does my RegEx work in PHP but fail in JavaScript?
Different programming languages utilize different RegEx engines (like PCRE for PHP vs. the ECMA engine for JavaScript). Certain advanced features like negative lookbehinds were historically unsupported in older JS environments.
How do I match special characters like a period or question mark?
Because those characters hold programmatic meaning in RegEx, they must be 'escaped' by placing a backslash before them (e.g., `.` or `?`).
Is it safe to paste API logs into this tester?
Yes. The testing environment runs purely in your local browser sandbox. We have zero visibility into the patterns or the text you are analyzing.