path-to-regexp

What is path-to-regexp?

The path-to-regexp package is a utility for converting paths to and from regular expressions. It is commonly used for routing in web applications, allowing developers to define patterns for URL paths and extract parameters from them.

What are path-to-regexp's main functionalities?

Path to RegExp Conversion

Convert a path string into a regular expression. It can also extract named parameter keys.

const { pathToRegexp } = require('path-to-regexp');
const keys = [];
const regexp = pathToRegexp('/user/:id', keys);

Extracting Parameters from a Path

Match a path against a pattern and extract the named parameters.

const { match } = require('path-to-regexp');
const matchFn = match('/user/:id');
const result = matchFn('/user/123');
// result.params will contain the extracted parameters

Compile Path to String

Compile a path function from a string pattern, which can then be used to construct paths with parameters.

const { compile } = require('path-to-regexp');
const toPath = compile('/user/:id');
const path = toPath({ id: 123 });
// path will be '/user/123'

Other packages similar to path-to-regexp

express

Express is a web application framework for Node.js that includes its own routing capabilities, which are similar to path-to-regexp. Express uses path-to-regexp internally for its routing logic.

react-router

React Router is a routing library for React that uses path-to-regexp-like pattern matching for defining routes and extracting parameters, but it is specifically tailored for React applications.

url-pattern

url-pattern is another library for matching URLs against patterns and extracting parameters. It offers a similar API to path-to-regexp but with different syntax and additional options for pattern matching.

README

Path-to-RegExp

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

Installation

npm install path-to-regexp --save

Usage

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

Parameters

Parameters match arbitrary strings in a path by matching up to the end of the segment, or up to any proceeding tokens. They are defined by prefixing a colon to the parameter name (:foo). Parameter names can use any valid JavaScript identifier, or be double quoted to use other characters (:"param-name").

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

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

Wildcard

Wildcard parameters match one or more characters across multiple segments. They are defined the same way as regular parameters, but are prefixed with an asterisk (*foo).

const fn = match("/*splat");

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

Optional

Braces can be used to define parts of the path that are optional.

const fn = match("/users{/:id}/delete");

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

fn("/users/123/delete");
//=> { path: '/users/123/delete', params: { id: '123' } }

Match

The match function returns a function for matching strings against a path:

• path String or array of strings.
• options (optional) (Extends pathToRegexp options)
  • 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. paths, hosts). It can not handle arbitrarily ordered data (e.g. query strings, URL fragments, JSON, etc).

PathToRegexp

The pathToRegexp function returns a regular expression for matching strings against paths. It

• path String or array of strings.
• 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)
  • delimiter The default delimiter for segments, e.g. [^/] for :named parameters. (default: '/')
  • trailing Allows optional trailing delimiter to match. (default: true)

const { regexp, keys } = pathToRegexp("/foo/:bar");

Compile ("Reverse" Path-To-RegExp)

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

• path A string.
• options (See parse for more options)
  • delimiter The default delimiter for segments, e.g. [^/] for :named parameters. (default: '/')
  • 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/caf%C3%A9"

const toPathRepeated = compile("/*segment");

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

// 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: "%3A%2F" }); //=> "/user/%3A%2F"

Stringify

Transform TokenData (a sequence of tokens) back into a Path-to-RegExp string.

• data A TokenData instance

const data = new TokenData([
  { type: "text", value: "/" },
  { type: "param", name: "foo" },
]);

const path = stringify(data); //=> "/:foo"

Developers

• 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, such as emoji, consider using encodeurl for encodePath.

Parse

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)
  • encodePath A function for encoding input strings. (default: x => x, recommended: encodeurl)

Tokens

TokenData is a sequence of tokens, currently of types text, parameter, wildcard, or group.

Custom path

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

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

Errors

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.

Unexpected ? or +

In past releases, ?, *, and + were used to denote optional or repeating parameters. As an alternative, try these:

• For optional (?), use an empty segment in a group such as /:file{.:ext}.
• For repeating (+), only wildcard matching is supported, such as /*path.
• For optional repeating (*), use a group and a wildcard parameter such as /files{/*path}.

Unexpected (, ), [, ], etc.

Previous versions of Path-to-RegExp used these for RegExp features. This version no longer supports them so they've been reserved to avoid ambiguity. To use these characters literally, escape them with a backslash, e.g. "\\(".

Missing parameter name

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

Unterminated quote

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

Express <= 4.x

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

• Regexp characters can no longer be provided.
• The optional character ? is no longer supported, use braces instead: /:file{.:ext}.
• Some characters have new meaning or have been reserved ({}?*+@!;).
• The parameter name now supports all JavaScript identifier characters, previously it was only [a-z0-9].

License

MIT