Turn a path string such as /user/:name into a regular expression.

npm install path-to-regexp --save

const { match, compile, parse } = require("path-to-regexp");

// match(path, options?)
// compile(path, options?)
// parse(path, options?)

The match function returns a function for transforming paths into parameters:

• path A string.
• options (optional) (See parse for more options)
  • sensitive Regexp will be case sensitive. (default: false)
  • end Validate the match reaches the end of the string. (default: true)
  • decode Function for decoding strings to params, or false to disable all processing. (default: decodeURIComponent)

const fn = match("/foo/:bar");

Please note: path-to-regexp is intended for ordered data (e.g. pathnames, hostnames). It can not handle arbitrarily ordered data (e.g. query strings, URL fragments, JSON, etc).

Parameters match arbitrary strings in a path by matching up to the end of the segment, or up to any proceeding tokens.

Named parameters are defined by prefixing a colon to the parameter name (:foo). Parameter names can use any valid unicode identifier characters, similar to JavaScript.

const fn = match("/:foo/:bar");

fn("/test/route");
//=> { path: '/test/route', params: { foo: 'test', bar: 'route' } }

Parameters can have a custom regexp, which overrides the default match ([^/] ). For example, you can match digits or names in a path:

const exampleNumbers = match("/icon-:foo(\\d ).png");

exampleNumbers("/icon-123.png");
//=> { path: '/icon-123.png', params: { foo: '123' } }

exampleNumbers("/icon-abc.png");
//=> false

const exampleWord = pathToRegexp("/(user|u)");

exampleWord("/u");
//=> { path: '/u', params: { '0': 'u' } }

exampleWord("/users");
//=> false

Tip: Backslashes need to be escaped with another backslash in JavaScript strings.

It is possible to define a parameter without a name. The name will be numerically indexed:

const fn = match("/:foo/(.*)");

fn("/test/route");
//=> { path: '/test/route', params: { '0': 'route', foo: 'test' } }

Parameters can be wrapped in {} to create custom prefixes or suffixes for your segment:

const fn = match("{/:attr1}?{-:attr2}?{-:attr3}?");

fn("/test");
//=> { path: '/test', params: { attr1: 'test' } }

fn("/test-test");
//=> { path: '/test-test', params: { attr1: 'test', attr2: 'test' } }

Modifiers are used after parameters with custom prefixes and suffixes ({}).

Parameters can be suffixed with a question mark (?) to make the parameter optional.

const fn = match("/:foo{/:bar}?");

fn("/test");
//=> { path: '/test', params: { foo: 'test' } }

fn("/test/route");
//=> { path: '/test/route', params: { foo: 'test', bar: 'route' } }

Parameters can be suffixed with an asterisk (*) to denote a zero or more parameter matches.

const fn = match("{/:foo}*");

fn("/foo");
//=> { path: '/foo', params: { foo: [ 'foo' ] } }

fn("/bar/baz");
//=> { path: '/bar/baz', params: { foo: [ 'bar', 'baz' ] } }

Parameters can be suffixed with a plus sign ( ) to denote a one or more parameter matches.

const fn = match("{/:foo} ");

fn("/");
//=> false

fn("/bar/baz");
//=> { path: '/bar/baz', params: { foo: [ 'bar', 'baz' ] } }

By default, parameters set the separator as the prefix suffix of the token. Using ; you can modify this:

const fn = match("/name{/:parts;-} ");

fn("/name");
//=> false

fn("/bar/1-2-3");
//=> { path: '/name/1-2-3', params: { parts: [ '1', '2', '3' ] } }

A wildcard is also supported. It is roughly equivalent to (.*).

const fn = match("/*");

fn("/");
//=> { path: '/', params: {} }

fn("/bar/baz");
//=> { path: '/bar/baz', params: { '0': [ 'bar', 'baz' ] } }

The compile function will return a function for transforming parameters into a valid path:

• path A string.
• options (See parse for more options)
  • sensitive Regexp will be case sensitive. (default: false)
  • validate When false the function can produce an invalid (unmatched) path. (default: true)
  • encode Function for encoding input strings for output into the path, or false to disable entirely. (default: encodeURIComponent)

const toPath = compile("/user/:id");

toPath({ id: "name" }); //=> "/user/name"
toPath({ id: "café" }); //=> "/user/café"

// When disabling `encode`, you need to make sure inputs are encoded correctly. No arrays are accepted.
const toPathRaw = compile("/user/:id", { encode: false });

toPathRaw({ id: ":/" }); //=> "/user/:/"
toPathRaw({ id: ":/" }); //=> Throws, "/user/:/" when `validate` is `false`.

const toPathRepeated = compile("{/:segment} ");

toPathRepeated({ segment: ["foo"] }); //=> "/foo"
toPathRepeated({ segment: ["a", "b", "c"] }); //=> "/a/b/c"

const toPathRegexp = compile("/user/:id(\\d )");

toPathRegexp({ id: "123" }); //=> "/user/123"

• If you are rewriting paths with match and compile, consider using encode: false and decode: false to keep raw paths passed around.
• To ensure matches work on paths containing characters usually encoded, consider using encodeurl for encodePath.

The parse function accepts a string and returns TokenData, the set of tokens and other metadata parsed from the input string. TokenData is can used with $match and $compile.

• path A string.
• options (optional)
  • delimiter The default delimiter for segments, e.g. [^/] for :named parameters. (default: '/')
  • encodePath A function for encoding input strings. (default: x => x, recommended: encodeurl for unicode encoding)

The tokens returned by TokenData is an array of strings or keys, represented as objects, with the following properties:

• name The name of the token
• prefix (optional) The prefix string for the segment (e.g. "/")
• suffix (optional) The suffix string for the segment (e.g. "")
• pattern (optional) The pattern defined to match this token
• modifier (optional) The modifier character used for the segment (e.g. ?)
• separator (optional) The string used to separate repeated parameters

In some applications, you may not be able to use the path-to-regexp syntax, but still want to use this library for match and compile. For example:

import { TokenData, match } from "path-to-regexp";

const tokens = ["/", { name: "foo" }];
const path = new TokenData(tokens, "/");
const fn = $match(path);

fn("/test"); //=> { path: '/test', index: 0, params: { foo: 'test' } }

An effort has been made to ensure ambiguous paths from previous releases throw an error. This means you might be seeing an error when things worked before.

In previous major versions / and . were used as implicit prefixes of parameters. So /:key? was implicitly {/:key}?. For example:

• /:key? → {/:key}? or /:key* → {/:key}* or /:key → {/:key}
• .:key? → {.:key}? or .:key* → {.:key}* or .:key → {.:key}
• :key? → {:key}? or :key* → {:key}* or :key → {:key}

Used as a custom separator for repeated parameters.

These characters have been reserved for future use.

Repeated parameters must have a separator to be valid. For example, {:foo}* can't be used. Separators can be defined manually, such as {:foo;/}*, or they default to the suffix and prefix with the parameter, such as {/:foo}*.

Parameter names, the part after :, must be a valid JavaScript identifier. For example, it cannot start with a number or dash. If you want a parameter name that uses these characters you can wrap the name in quotes, e.g. :"my-name".

Parameter names can be wrapped in double quote characters, and this error means you forgot to close the quote character.

Parameters in path-to-regexp must be basic groups. However, you can use features that require the ? nested within the pattern. For example, :foo((?!login)[^/] ) is valid, but :foo(?!login) is not.

A parameter pattern can not contain nested capturing groups.

A parameter pattern must have the expected number of parentheses. An unbalanced amount, such as ((?!login) implies something has been written that is invalid. Check you didn't forget any parentheses.

Path-To-RegExp breaks compatibility with Express <= 4.x in the following ways:

• The only part of the string that is a regex is within ().
  • In Express.js 4.x, everything was passed as-is after a simple replacement, so you could write /[a-z] to match /test.
• The ? optional character must be used after {}.
• Some characters have new meaning or have been reserved ({}?* @!;).
• The parameter name now supports all unicode identifier characters, previously it was only [a-z0-9].

MIT