User:Steve0Greatness/drafts/Regular expression

The alternating yellow and orange highlights show results for the following regexp pattern: /[a-z](?<![aeiou])[aeiou]/gi (any consonant-vowel pair)

Regular expression, often shorted to regex, is used to specify a match pattern with just text.

Syntax

x, y, and z when used under symbols are placeholders for text. Capital Xs, Ys, and Zs are used for number placeholders.

Syntax Reference

Symbol(s)	Name	Description	Example
Groups and backreferences
(x)	Capture group	Separates the content in the output.	"Foo Bar" /(Foo)|(Bar)/g -> [ "Foo", "Bar" ]
(?:x)	Non-capture group	Acts as if the parentheses were not there	"Foo Bar" /(?:Foo)|(?:Bar)/g -> [ "Foo Bar" ]
(?<y>x)	Named capture group	Equivalent to (x), except it remembers the content used.	"Foo Bar" /(?<F>Foo)|(?<B>Bar)/g -> [ "Foo", "Bar" ]
\k<y>	Named backreference	References a previous named capture group, note that \k is literal	"Foo Foo" /(?<Foo>Foo)\s\k<Foo>/g -> [ "Foo Foo" ]
Character classes
[x-z]	Character class	Matches every letter or number from x to z.	"Foo Bar" /[a-f]/gi -> [ "F", "B", "a" ]
[xyz]		References either x, y, or z	"Foo Bar" /[FB]/g -> [ "F", "B" ]
[^x-z]	Negated character class	Matches every letter or number not from x to z.	"Foo Bar" /[^a-f]/gi -> [ "o", "o", " ", "r" ]
[^xyz]		References characters that aren't x, y, or z	"Foo Bar" /[^FB]/g -> [ "o", "o", " ", "a", "r" ]
.	Wildcard	Matches every character besides line terminators. Line terminators include \n, \r, \u2028, and \u2029	"Foo Bar" /./g -> [ "F", "o", "o", " ", "B", "a", "r" ]
x|y	Disjunction	Match something or something else.	"Foo Bar" /Foo|Bar/g -> [ "Foo", "Bar" ]
\	Escape character	If a character is reserved for regex, such as *, |, or .. Note that this is itself a reserve character, so to match for it, you need to use \\.	"Foo.bar apple 78.9 banana" /[A-Za-z0-9]*\.[A-Za-z0-9]*/g -> [ "Foo.bar", "78.9" ]
\d	Digit character class escape	Equivalent to [0-9]	"78 Foo Bars" /\d/g -> [ "7", "8" ]
\D	Non-digit character class escape	Equivalent to [^0-9]	"78 Foo Bars" /\d/g -> [ "F", "o"," "o", " ", "B", "a", "r", "s" ]
\w	Word character class escape	Equivalent to [A-Za-z0-9_]	"_Foo- Bars+" /\d/g -> [ "_", "F"," "o", "o", "B", "a", "r", "s" ]
\W	Non-word character class escape	Equivalent to [^A-Za-z0-9_]	"_Foo- Bars+" /\d/g -> [ "-", " ", "+" ]
\s	White space character class escape	Matches all whitespace characters. Equivalent to [\f\n\r\t\v\u0020\u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff]	"_Foo- Bars+" /\d/g -> [ "-", " ", "+" ]
\S	Non-white space character class escape	Matches everything but whitespace characters. Equivalent to [^\f\n\r\t\v\u0020\u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff]	"_Foo- Bars+" /\d/g -> [ "-", " ", "+" ]
\t	Horizontal tab escape	Matches horizontal tab characters.	"a    b" /\t/g -> [ "    " ]
\n	Linefeed escape	Matches linefeed/new line characters	"a b" /(?:\r?\n)|(?:\v)|(?:\f)/g -> [ "" ]
\r	Carriage return escape	Matches carriage return characters
\v	Vertical tab escape	Matches vertical tab characters
\f	Form feed escape	Matches form feed characters
[\b]	Backspace escape	Matches backspace	No example can be provided
\0	NUL escape	Matches the NUL character
\u{YYYY} or \u{YYYY}	Unicode value escape	When the u flag is applied. Here Y represents a hexadecimal number.
\uYYYY		Matches provided UTF-16 hexadecimal value. Represented with Ys here.
\p{x} or \P{x}	Unicode character class escape	Matches a character based on the Unicode property (x).
\cx	Caret notation escape	Matches the sequence following \c with caret notation. Note that x represents a sequence of characters here, rather than a single one.	"a b" /\cM\cJ//g -> [ "" ]
Assertions
^	Input boundary beginning assertion	Matches the beginning of the input. If the m flag is on, it matches the start of each line.	"Foo Bar" /^Foo Bar$/g -> [ "Foo Bar" ]
$	Input boundary end assertion	Matches the end of the input. If the m flag is on, it matches the end of each line.
\b	Word boundary assertion	Matches either end of a word.	"Foo Bar" /(\bFoo\b)/ -> [ "Foo" ]
\B	Non-word boundary assertion	Matches the middle of a word.	"Foo Bar" /(B\Bar)/ -> [ "Bar" ]

Flags

Flag	Name	Description
g	global	Search all of a string, rather than stopping once you find an occurrence.

See also

• (Match [foo bar] with regex [foo] [g] :: operators)
• <Test regex [foo bar] [g] with text [foo] :: sensing>

External links

• Regular expressions on Wikipedia
• TurboWarp extension gallery featuring TrueFantom's RegExp extension. It can be loaded into PenguinMod using https://extensions.turbowarp.org/true-fantom/regexp.js as the URL in the Load Custom Extensions popup. It adds more regex functionality into PenguinMod.
• regex101, fairly useful little app with some fun challenges to test your knowledge of regex.
• MDN's Regular expressions documentation for JavaScript. There wasn't a good place to cite this, but I sourced at lot of stuff from here. Pretty much all of the names for each syntax element.