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

npm install path-to-regexp --save 

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 allows 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. (default: '/')
  • endsWith Optional character, or list of characters, to treat as "end" characters.
  • whitelist List of characters to consider delimiters when parsing. (default: undefined, any character)

const keys = []; const regexp = pathToRegexp("/foo/:bar", keys); // regexp = /^\/foo\/([^\/]+?)\/?$/i // keys = [{ name: 'bar', prefix: '/', delimiter: '/', optional: false, repeat: false, pattern: '[^\\/]+?' }]

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).

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

Named parameters are defined by prefixing a colon to the parameter name (:foo). By default, the parameter will match until the next prefix (e.g. [^/]+).

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_]).

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

const regexp = pathToRegexp("/:foo/:bar?"); // keys = [{ name: 'foo', ... }, { name: 'bar', delimiter: '/', optional: true, repeat: false }] 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.

Parameters can be suffixed with an asterisk (*) to denote a zero or more parameter matches. The prefix is used for each match.

const regexp = pathToRegexp("/:foo*"); // keys = [{ name: 'foo', delimiter: '/', optional: true, repeat: true }] regexp.exec("/"); //=> [ '/', undefined, index: 0, input: '/', groups: undefined ] regexp.exec("/bar/baz"); //=> [ '/bar/baz', 'bar/baz', index: 0, input: '/bar/baz', groups: undefined ]

Parameters can be suffixed with a plus sign (+) to denote a one or more parameter matches. The prefix is used for each match.

const regexp = pathToRegexp("/:foo+"); // keys = [{ name: 'foo', delimiter: '/', optional: false, repeat: true }] regexp.exec("/"); //=> null regexp.exec("/bar/baz"); //=> [ '/bar/baz','bar/baz', index: 0, input: '/bar/baz', groups: undefined ]

It is possible to write an unnamed parameter that only consists of a matching group. It works the same as a 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 ]

All 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.

The match function will return a function for transforming paths into parameters:

const match = match("/user/:id"); match("/user/123"); //=> { path: '/user/123', index: 0, params: { id: '123' } } match("/invalid"); //=> false

The normalizePathname function will return a normalized string for matching with pathToRegexp:

const re = pathToRegexp("/caf\u00E9"); const input = encodeURI("/caf\u00E9"); re.test(input); //=> false re.test(normalizePathname(input)); //=> true

Note: It may be preferable to implement something in your own library that normalizes the pathname for matching. E.g. URL automatically URI encodes paths for you, which would result in a consistent match.

Tip: Consider using String.prototype.normalize to resolve unicode variants of the same string.

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: '/', delimiter: '/', optional: false, repeat: false, pattern: '[^\\/]+?' } console.log(tokens[2]); //=> { name: 0, prefix: '/', delimiter: '/', optional: false, repeat: false, pattern: '.*' }

Note: This method only works with strings.

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

const toPath = compile("/user/:id"); toPath({ id: 123 }); //=> "/user/123" toPath({ id: "café" }); //=> "/user/caf%C3%A9" toPath({ id: "/" }); //=> "/user/%2F" toPath({ id: ":/" }); //=> "/user/%3A%2F" toPath({ id: ":/" }, { encode: (value, token) => value, 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. It will do all necessary checks to ensure the generated path is valid. This method only works with strings.

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.

• name The name of the token (string for named or number for unnamed index)
• prefix The prefix character for the segment (e.g. /)
• delimiter The delimiter for the segment (same as prefix or default delimiter)
• optional Indicates the token is optional (boolean)
• repeat Indicates the token is repeated (boolean)
• pattern The RegExp used to match this token (string)

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*)

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

MIT