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 a standard

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" ]

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.