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正規表現テスト
UtilBrix が提供JavaScript regular expressions. Processing runs in a worker and stops after 3 seconds. Quick reference: \d digit, \w word, \s whitespace, + one or more, * zero or more, ^ start, $ end.
詳しい方法と使用例は英語で提供しています。
Step-by-step instructions (English)
- Enter a JavaScript regular-expression pattern and the desired flags.
- Paste representative test text, including examples that should not match.
- Optionally enter a replacement string, then inspect matches, groups, indexes, and replacement output.
計算式と方法
The browser executes JavaScript RegExp semantics in a dedicated worker. Match details include text, zero-based UTF-16 indexes, captured groups, and named groups. The replacement string follows JavaScript replacement conventions, including $1 and named references.
使用例
The pattern \d+ with flag g finds 12 and 34 in order 12, item 34. A worker timeout stops patterns that take too long.
When this tool is useful
Develop a pattern for text extraction or cleanup before adding it to an application. Testing both matching and nonmatching examples helps catch a pattern that works on one sample but accepts too much.
Common mistakes and limitations
- Regular-expression syntax and flags differ between languages; this tool uses JavaScript semantics.
- A pattern can be expensive on long input. The worker time limit protects the page, but a timeout means the pattern needs review.
Practical questions about this tool (English)
Why am I seeing only one match?
Check the global g flag if you intend to find repeated matches. Other flags such as i and m affect case sensitivity and line boundaries rather than enabling all matches.
What do match indexes count?
Indexes are zero-based UTF-16 positions, matching JavaScript string indexing. Some visible symbols occupy multiple code units, so the index can differ from a visual character count.