@smikhalevski/route-pattern

route-pattern

The path pattern parser, that supports named variables, variable constraints, bash-like alternation, regular expressions, and wildcards.

This package is tiny, just 2.2 kB gzipped including dependencies.

npm install --save-prod @smikhalevski/route-pattern

Usage

import {convertPatternToRegExp} from '@smikhalevski/route-pattern';

const re = convertPatternToRegExp('/(\\d+)/:foo{ bar, qux }');
const match = re.exec('/123/bar');

console.log(match?.groups?.foo); // → 'bar'

The support of named capturing groups is not required from the environment.

Features

/foo/bar is a literal path that is matched as is.

Spaces, tabs, and newlines are ignored, so / foo / bar is the same as /foo/bar, and /foo bar is the same as /foobar (note the absent spaces).

If you want to preserve spaces, use quotes: /" foo bar".

Regular expression

(\\d+) declares a regular expression, spaces have meaning inside a regular expression.

RegExps can contain a named capturing groups which are merged with variables. For example, /:foo/(?<bar>abc) would match /123/abc and groups would be {foo: '123', bar: 'abc'}.

Wildcards

* declares a wildcard that matches everything except the path separator. For example, /foo/*/bar would match /foo/okay/bar and /foo//bar but won't match /foo/no/sir/bar.

** declares a greedy wildcard that matches everything, even path separators. For example, /foo/**/bar would match /foo/okay/bar, /foo//bar and /foo/no/sir/bar.

If you want to match at least one character, use a regular expression instead of a wildcard. For example, /foo/([^/]+)/bar would match /foo/okay/bar and won't match /foo//bar.

Alternation

{ foo, bar } declares an alternation: foo or bar.

Alternation supports nesting, for example /foo{ -bar, /(\\d+)/qux } would match /foo-bar and /foo/123/qux.

Variables

:foo declares a variable. Variable name should match ^[A-Za-z0-9$_]+$.

By default, variables match everything except the path separator.

A single pattern that immediately follows the variable declaration is treated as a variable constraint. For example,:foo bar and :foo"bar" would both read variable foo and treat bar as its string literal constraint.

:foo(\\d+) declares a variable whose value is constrained by a regular expression.

:foo{ a, b } declares a variable whose value is constrained by an alternation.

:foo{**} variables can be constrained with wildcards.

Variables can be nested through an alternation: /aaa/ :foo{ /bbb, /ccc/:bar }.

Variables are not treated as constraints for other variables. For example, :foo:bar{abc} would match 123abc and groups would be {foo: '123', bar: 'abc'}.