测试正则表达式并实时查看匹配结果。
Regular expressions (regex) are sequences of characters that define search patterns. They're used for string matching, searching, and text manipulation. Regex is supported in virtually all programming languages and many text editors. While powerful, regex syntax can be complex and requires practice to master.
Regex uses literal characters and metacharacters. Common metacharacters include: . (any character), * (zero or more), + (one or more), ? (optional), ^ (start), $ (end), [] (character class), () (grouping), | (alternation). Escape special characters with backslash.
Regex flavors vary between implementations. JavaScript, Python, and PCRE have subtle differences in supported features. Always test your regex in the target environment.
Avoid catastrophic backtracking by using specific character classes instead of .*, use anchors (^ and $), and prefer possessive quantifiers when available. Profile complex patterns with large inputs.