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Description

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

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Path-to-RegExp

Turn a path string such as

/user/:name
into a regular expression.

NPM version Build status Test coverage Dependency Status License Downloads

Installation

npm install path-to-regexp --save

Usage

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

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

  • path A string, array of strings, or a regular expression.
  • keys An array to populate with keys found in the path.
  • options
    • sensitive When
      true
      the regexp will be case sensitive. (default:
      false
      )
    • strict When
      true
      the regexp won't allow an optional trailing delimiter to match. (default:
      false
      )
    • end When
      true
      the regexp will match to the end of the string. (default:
      true
      )
    • start When
      true
      the regexp will match from the beginning of the string. (default:
      true
      )
    • delimiter The default delimiter for segments, e.g.
      [^/#?]
      for
      :named
      patterns. (default:
      '/#?'
      )
    • endsWith Optional character, or list of characters, to treat as "end" characters.
    • encode A function to encode strings before inserting into
      RegExp
      . (default:
      x => x
      )
    • prefixes List of characters to automatically consider prefixes when parsing. (default:
      ./
      )
const keys = [];
const regexp = pathToRegexp("/foo/:bar", keys);
// regexp = /^\/foo(?:\/([^\/#\?]+?))[\/#\?]?$/i
// keys = [{ name: 'bar', prefix: '/', suffix: '', pattern: '[^\\/#\\?]+?', modifier: '' }]

Please note: The

RegExp
returned by
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). When using paths that contain query strings, you need to escape the question mark (
?
) to ensure it does not flag the parameter as optional.

Parameters

The path argument is used to define parameters and populate keys.

Named Parameters

Named parameters are defined by prefixing a colon to the parameter name (

:foo
).
const regexp = pathToRegexp("/:foo/:bar");
// keys = [{ name: 'foo', prefix: '/', ... }, { name: 'bar', prefix: '/', ... }]

regexp.exec("/test/route"); //=> [ '/test/route', 'test', 'route', index: 0, input: '/test/route', groups: undefined ]

Please note: Parameter names must use "word characters" (

[A-Za-z0-9_]
).
Custom Matching Parameters

Parameters can have a custom regexp, which overrides the default match (

[^/]+
). For example, you can match digits or names in a path:
const regexpNumbers = pathToRegexp("/icon-:foo(\\d+).png");
// keys = [{ name: 'foo', ... }]

regexpNumbers.exec("/icon-123.png"); //=> ['/icon-123.png', '123']

regexpNumbers.exec("/icon-abc.png"); //=> null

const regexpWord = pathToRegexp("/(user|u)"); // keys = [{ name: 0, ... }]

regexpWord.exec("/u"); //=> ['/u', 'u']

regexpWord.exec("/users"); //=> null

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

Custom Prefix and Suffix

Parameters can be wrapped in

{}
to create custom prefixes or suffixes for your segment:
const regexp = pathToRegexp("/:attr1?{-:attr2}?{-:attr3}?");

regexp.exec("/test"); // => ['/test', 'test', undefined, undefined]

regexp.exec("/test-test"); // => ['/test', 'test', 'test', undefined]

Unnamed Parameters

It is possible to write an unnamed parameter that only consists of a regexp. It works the same the named parameter, except it will be numerically indexed:

const regexp = pathToRegexp("/:foo/(.*)");
// keys = [{ name: 'foo', ... }, { name: 0, ... }]

regexp.exec("/test/route"); //=> [ '/test/route', 'test', 'route', index: 0, input: '/test/route', groups: undefined ]

Modifiers

Modifiers must be placed after the parameter (e.g.

/:foo?
,
/(test)?
,
/:foo(test)?
, or
{-:foo(test)}?
).
Optional

Parameters can be suffixed with a question mark (

?
) to make the parameter optional.
const regexp = pathToRegexp("/:foo/:bar?");
// keys = [{ name: 'foo', ... }, { name: 'bar', prefix: '/', modifier: '?' }]

regexp.exec("/test"); //=> [ '/test', 'test', undefined, index: 0, input: '/test', groups: undefined ]

regexp.exec("/test/route"); //=> [ '/test/route', 'test', 'route', index: 0, input: '/test/route', groups: undefined ]

Tip: The prefix is also optional, escape the prefix

\/
to make it required.

When dealing with query strings, escape the question mark (

?
) so it doesn't mark the parameter as optional. Handling unordered data is outside the scope of this library.
const regexp = pathToRegexp("/search/:tableName\\?useIndex=true&term=amazing");

regexp.exec("/search/people?useIndex=true&term=amazing"); //=> [ '/search/people?useIndex=true&term=amazing', 'people', index: 0, input: '/search/people?useIndex=true&term=amazing', groups: undefined ]

// This library does not handle query strings in different orders regexp.exec("/search/people?term=amazing&useIndex=true"); //=> null

Zero or more

Parameters can be suffixed with an asterisk (

*
) to denote a zero or more parameter matches.
const regexp = pathToRegexp("/:foo*");
// keys = [{ name: 'foo', prefix: '/', modifier: '*' }]

regexp.exec("/"); //=> [ '/', undefined, index: 0, input: '/', groups: undefined ]

regexp.exec("/bar/baz"); //=> [ '/bar/baz', 'bar/baz', index: 0, input: '/bar/baz', groups: undefined ]

One or more

Parameters can be suffixed with a plus sign (

+
) to denote a one or more parameter matches.
const regexp = pathToRegexp("/:foo+");
// keys = [{ name: 'foo', prefix: '/', modifier: '+' }]

regexp.exec("/"); //=> null

regexp.exec("/bar/baz"); //=> [ '/bar/baz','bar/baz', index: 0, input: '/bar/baz', groups: undefined ]

Match

The

match
function will return a function for transforming paths into parameters:
// Make sure you consistently `decode` segments.
const match = match("/user/:id", { decode: decodeURIComponent });

match("/user/123"); //=> { path: '/user/123', index: 0, params: { id: '123' } } match("/invalid"); //=> false match("/user/caf%C3%A9"); //=> { path: '/user/caf%C3%A9', index: 0, params: { id: 'café' } }

Process Pathname

You should make sure variations of the same path match the expected

path
. Here's one possible solution using
encode
:
const match = match("/café", { encode: encodeURI, decode: decodeURIComponent });

match("/user/caf%C3%A9"); //=> { path: '/user/caf%C3%A9', index: 0, params: { id: 'café' } }

Note:

URL
automatically encodes pathnames for you.

Alternative Using Normalize

Sometimes you won't have an already normalized pathname. You can normalize it yourself before processing:

/**
 * Normalize a pathname for matching, replaces multiple slashes with a single
 * slash and normalizes unicode characters to "NFC". When using this method,
 * `decode` should be an identity function so you don't decode strings twice.
 */
function normalizePathname(pathname: string) {
  return (
    decodeURI(pathname)
      // Replaces repeated slashes in the URL.
      .replace(/\/+/g, "/")
      // Reference: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/normalize
      // Note: Missing native IE support, may want to skip this step.
      .normalize()
  );
}

// Two possible ways of writing /café: const re = pathToRegexp("/caf\u00E9"); const input = encodeURI("/cafe\u0301");

re.test(input); //=> false re.test(normalizePathname(input)); //=> true

Parse

The

parse
function will return a list of strings and keys from a path string:
const tokens = parse("/route/:foo/(.*)");

console.log(tokens[0]); //=> "/route"

console.log(tokens[1]); //=> { name: 'foo', prefix: '/', suffix: '', pattern: '[^\/#\?]+?', modifier: '' }

console.log(tokens[2]); //=> { name: 0, prefix: '/', suffix: '', pattern: '.*', modifier: '' }

Note: This method only works with strings.

Compile ("Reverse" Path-To-RegExp)

The

compile
function will return a function for transforming parameters into a valid path:
// Make sure you encode your path segments consistently.
const toPath = compile("/user/:id", { encode: encodeURIComponent });

toPath({ id: 123 }); //=> "/user/123" toPath({ id: "café" }); //=> "/user/caf%C3%A9" toPath({ id: "/" }); //=> "/user/%2F"

toPath({ id: ":/" }); //=> "/user/%3A%2F"

// Without encode, you need to make sure inputs are encoded correctly. const toPathRaw = compile("/user/:id");

toPathRaw({ id: "%3A%2F" }); //=> "/user/%3A%2F" toPathRaw({ id: ":/" }, { validate: false }); //=> "/user/:/"

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" toPathRegexp({ id: "123" }); //=> "/user/123" toPathRegexp({ id: "abc" }); //=> Throws TypeError. toPathRegexp({ id: "abc" }, { validate: false }); //=> "/user/abc"

Note: The generated function will throw on invalid input.

Working with Tokens

Path-To-RegExp exposes the two functions used internally that accept an array of tokens:

  • tokensToRegexp(tokens, keys?, options?)
    Transform an array of tokens into a matching regular expression.
  • tokensToFunction(tokens)
    Transform an array of tokens into a path generator function.

Token Information

  • name
    The name of the token (
    string
    for named or
    number
    for unnamed index)
  • prefix
    The prefix string for the segment (e.g.
    "/"
    )
  • suffix
    The suffix string for the segment (e.g.
    ""
    )
  • pattern
    The RegExp used to match this token (
    string
    )
  • modifier
    The modifier character used for the segment (e.g.
    ?
    )

Compatibility with Express <= 4.x

Path-To-RegExp breaks compatibility with Express <=

4.x
:
  • RegExp special characters can only be used in a parameter
    • Express.js 4.x supported
      RegExp
      special characters regardless of position - this is considered a bug
  • Parameters have suffixes that augment meaning -
    *
    ,
    +
    and
    ?
    . E.g.
    /:user*
  • No wildcard asterisk (
    *
    ) - use parameters instead (
    (.*)
    or
    :splat*
    )

Live Demo

You can see a live demo of this library in use at express-route-tester.

License

MIT

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