Constructs

These functions and objects represent available regex constructs.

choiceOf()

function choiceOf(
  ...alternatives: RegexSequence[],
): RegexConstruct {

Regex syntax: a|b|c.

The choiceOf (disjunction) construct matches one out of several possible sequences. It functions similarly to a logical OR operator in programming. It can match simple string options as well as complex patterns.

Example: choiceOf("color", "colour") matches either color or colour pattern.

regex()

function regex(sequence: RegexSequence): RegexConstruct;

Regex syntax: the pattern remains unchanged when wrapped by this construct.

This construct is a no-op operator that groups array of RegexElements into a single element for composition purposes. This is particularly useful for defining smaller sequence patterns as separate variables.

Without regex():

const exponent = [anyOf('eE'), optional(anyOf('+-')), oneOrMore(digit)];
const numberWithExponent = buildRegExp([
  oneOrMore(digit),
  ...exponent, // Need to spread "exponent" as it's an array.
]);

With regex():

const exponent = regex([anyOf('eE'), optional(anyOf('+-')), oneOrMore(digit)]);
const numberWithExponent = buildRegExp([
  oneOrMore(digit),
  exponent, // Easily compose "exponent" sequence as a single element.
]);