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Assertions

Anchors​

Anchors are special characters or sequences that specify positions in the input string rather than matching specific characters.

Start and end of string​

const startOfString: RegexConstruct;
const endOfString: RegexConstruct;
  • startOfString anchor matches the start of a string (or line, if multiline mode is enabled). Regex syntax: ^.
  • endOfString anchor matches the end of a string (or line, if multiline mode is enabled). Regex syntax: $.

Word boundary​

This API was added in version 1.3.0.

const wordBoundary: RegexConstruct;
const nonWordBoundary: RegexConstruct;
  • wordBoundary matches the positions where a word character is not followed or preceded by another word character, effectively indicating the start or end of a word. Regex syntax: \b.
  • nonWordBoundary matches the positions where a word character is followed or preceded by another word character, indicating that it is not at the start or end of a word. Regex syntax: \B.

Note: word characters are letters, digits, and underscore (_). Other special characters like #, $, etc are not considered word characters.

Lookarounds​

Lookarounds in regex are used for asserting that some pattern is or isn't followed or preceded by another pattern, without including the latter in the match.

lookahead()​

This API was added in version 1.3.0.

function lookahead(sequence: RegexSequence): RegexConstruct;

Regex syntax: (?=...).

Allows for conditional matching by checking for subsequent patterns in regexes without consuming them.

negativeLookahead()​

This API was added in version 1.3.0.

function negativeLookahead(sequence: RegexSequence): RegexConstruct;

Regex syntax: (?!...).

Allows for matches to be rejected if a specified subsequent pattern is present, without consuming any characters.

lookbehind()​

This API was added in version 1.3.0.

function lookbehind(sequence: RegexSequence): RegexConstruct;

Regex syntax: (?<=...).

Allows for conditional matching by checking for preceeding patterns in regexes without consuming them.

negativeLookbehind()​

This API was added in version 1.3.0.

function negativeLookahead(sequence: RegexSequence): RegexConstruct;

Regex syntax: (?<!...).

Allows for matches to be rejected if a specified preceeding pattern is present, without consuming any characters.