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Regex
Regular expressions in PCRE, JavaScript and Python.
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JavaScript regex flags: g, i, m, s, u, v, y and d
What each JavaScript RegExp flag does: g finds all matches, i ignores case, m works per line, s lets . match newlines, u and v add Unicode, plus y and d.
All Regex flags & options
Regex cheat sheet: characters, quantifiers, groups and lookarounds
Regex cheat sheet: character classes, anchors, quantifiers, greedy and lazy matching, groups and backreferences, lookarounds, with tested Python examples.
All Regex cheat sheets
Regex features by engine: JavaScript, Python, PCRE and POSIX ERE
Which regex features work where: lookbehind, named groups, \p{L}, atomic groups and possessive quantifiers in JavaScript, Python re, PCRE and POSIX ERE, tested.
All Regex compatibility
Regex shorthand classes: \d \w \s \b and POSIX [:alpha:]
What regex shorthand classes match: digits, word characters, whitespace and word boundaries, their uppercase opposites, POSIX classes and Unicode rules.
All Regex codes & tables
Greedy vs lazy quantifiers in regex
A greedy quantifier such as .* matches as much as it can and backtracks only when needed; a lazy one such as .*? matches as little as possible. Examples.
All Regex glossary
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