Overview

TS Regex Builder allows you to build complex regular expressions using domain-specific language.

Terminology

• regex construct (RegexConstruct) - common name for all regex constructs like character classes, quantifiers, and anchors.
• regex element (RegexElement) - a fundamental building block of a regular expression, defined as either a regex construct, a string, or RegExp literal (/.../).
• regex sequence (RegexSequence) - a sequence of regex elements forming a regular expression. For developer convenience, it also accepts a single element instead of an array.

Most of the regex constructs accept a regex sequence as their argument.

Examples of sequences

• single element (construct): capture('Hello')
• single element (string): 'Hello'
• single element (RegExp literal): /Hello/
• array of elements: ['USD', oneOrMore(digit), /Hello/]

Regex constructs can be composed into a tree structure:

const currencyCode = repeat(/[A-Z]/, 3); // or repeat(charRange('A', 'Z'), 3);

const currencyAmount = buildRegExp([
  choiceOf('$', '€', currencyCode), // currency
  capture(
    oneOrMore(digit), // integer part
    optional(['.', repeat(digit, 2)]), // fractional part
  ),
]);

See Types for more info.

Regex Builders

Builder	Regex Syntax	Description
buildRegExp(...)	/.../	Create RegExp instance
buildRegExp(..., { ignoreCase: true })	/.../i	Create RegExp instance with flags

See Builder for more info.

Regex Constructs

Construct	Regex Syntax	Notes
choiceOf(x, y, z)	x|y|z	Match one of provided sequences
capture(...)	(...)	Create a capture group

See Constructs for more info.

note

TS Regex Builder does not have a construct for non-capturing groups. Such groups are implicitly added when required.

Quantifiers

Quantifier	Regex Syntax	Description
zeroOrMore(x)	x*	Zero or more occurrence of a pattern
oneOrMore(x)	x+	One or more occurrence of a pattern
optional(x)	x?	Zero or one occurrence of a pattern
repeat(x, n)	x{n}	Pattern repeats exact number of times
repeat(x, { min: n, })	x{n,}	Pattern repeats at least given number of times
repeat(x, { min: n, max: n2 })	x{n1,n2}	Pattern repeats between n1 and n2 number of times

See Quantifiers for more info.

Assertions

Assertion	Regex Syntax	Description
startOfString	^	Match the start of the string (or the start of a line in multiline mode)
endOfString	$	Match the end of the string (or the end of a line in multiline mode)
wordBoundary	\b	Match the start or end of a word without consuming characters
lookahead(...)	(?=...)	Match subsequent text without consuming it
negativeLookahead(...)	(?!...)	Reject subsequent text without consuming it
lookbehind(...)	(?<=...)	Match preceding text without consuming it
negativeLookbehind(...)	(?<!...)	Reject preceding text without consuming it

See Assertions for more info.

Character classes

::: tip

You may also use inline regexes for specifying character classes, as they offer a concise yet readable syntax. For example, /[a-z0-9_]/.

:::

Character class	Regex Syntax	Description
any	.	Any character
word	\w	Word character: letter, digit, underscore
digit	\d	Digit character: 0 to 9
whitespace	\s	Whitespace character: space, tab, line break, ...
anyOf('abc')	[abc]	Any of provided characters
charRange('a', 'z')	[a-z]	Character in a range
charClass(...)	[...]	Union of multiple character classes
negated(...)	[^...]	Negation of a given character class

See Character Classes and Unicode for more info.