javascript :: Match

Regular expression validation

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Pattern Cheatsheet

Special Sequences

\w	Any "word" character (a-z 0-9 _)
\W	Any non "word" character
\s	Whitespace (space, tab CRLF)
\S	Any non whitepsace character
\d	Digits (0-9)
\D	Any non digit character
.	Any character except newline

n*	Zero or more of n
n+	One or more of n
n?	Zero or one occurrences of n
{n}	n occurrences exactly
{n,}	At least n occurrences
{,m}	At most m occurrences
{n,m}	Between n and m occurrences (inclusive)

Point based assertions

\b	Word boundary
\B	Not a word boundary
\A	Start of subject
\Z	End of subject or newline at end
\z	End of subject
\G	First matching position in subject

Pattern Modifiers

i	Case Insensitive
m	Multiline mode - ^ and $ match start and end of lines
s	Dotall - . class includes newline
x	Extended– comments and whitespace
e	preg_replace(PHP) only – enables evaluation of replacement as PHP code
S	Extra analysis of pattern
U	Pattern is ungreedy
u	Pattern is treated as UTF-8

Meta Characters

^	Start of subject (or line in multiline mode)
$	End of subject (or line in multiline mode)
[	Start character class definition
]	End character class definition
\|	Alternates, eg (a\|b) matches a or b
(	Start subpattern
)	End subpattern
\	Escape character

\n	newline
\r	carriage return
\t	tab
\xhh	character with hex code hh
\ddd	character with octal code ddd

(?=)	Positive look ahead assertion foo(?=bar) matches foo when followed by bar
(?!)	Negative look ahead assertion foo(?!bar) matches foo when not followed by bar
(?<=)	Positive look behind assertion (?<=foo)bar matches bar when preceded by foo
(?	Negative look behind assertion (?
(?>)	Once-only subpatterns (?>\d+)bar Performance enhancing when bar not present
(?(x))	Conditional subpatterns
(?(3)foo\|fu)bar	Matches foo if 3rd subpattern has matched, fu if not
(?#)	Comment (?# Pattern does x y or z)