A type-safe pattern builder & route matching library written in TypeScript

router, pattern, path, ts, typescript
npm install chemin@4.1.1


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A type-safe pattern builder & route matching library written in TypeScript


import { Chemin } from 'chemin';

const chemin = Chemin.parse('/admin/post/:postId/delete?');

// => false

// => { rest: [], params: { postId: 'e5t89u', delete: false } }

More advanced (and type-safe) patterns

Use the Chemin.create and CheminParam to build more complex type-safe paths !

import { Chemin, CheminParam as P } from 'chemin';

const chemin = Chemin.create('admin', 'post', P.number('postId'), P.optionalConst('delete'));

// => false

const match = chemin.match('/admin/post/45');
// => { rest: [], params: { postId: 45, delete: false } }


You can use a Chemin inside another to easily compose your routes !

import { Chemin, CheminParam as P } from 'chemin';

const postFragment = Chemin.create('post', P.number('postId'));
const postAdmin = Chemin.create('admin', P.string('userId'), postFragment, 'edit');

console.log(postAdmin.toString()); // /admin/:userId/post/:postId(number)/edit

Custom CheminParam

You can create your own CheminParam to better fit your application while keeping full type-safety !

import { Chemin, CheminParam } from 'chemin';

// match only string of 4 char [a-z0-9]
function fourCharStringId<N extends string>(name: N): CheminParam<N, string> {
  const reg = /^[a-z0-9]{4}$/;
  return {
    match: (...all) => {
      if (all[0].match(reg)) {
        return { match: true, value: all[0], next: all.slice(1) };
      return { match: false, next: all };
    serialize: value => value,
    toString: () => `:${name}(id4)`,

const path = Chemin.create('item', fourCharStringId('itemId'));
console.log(path.match('/item/a4e3t')); // false (5 char)
console.log(path.match('/item/A4e3')); // false (Maj)
console.log(path.match('/item/a4e3')); // { rest: [], params: { itemId: 'a4e3' } }

Take a look a the custom-advanced.ts example. and the build-in CheminParam.



Parse a string into a Chemin object

Accepts a string (/admin/:user/edit?) and return a Chemin.

Supported patterns

  • admin: Create a CheminParam.constant('admin')
  • :param: Create a CheminParam.string('param')
  • maybe?: Create a CheminParam.optionalConst('maybe')
  • :maybe?: Create a CheminParam.optionalString('maybe')


Create a Chemin

Accepts any number or arguments of type string, CheminParam or Chemin.

Note: strings are converted to CheminParam.constant.

Chemin.create('admin', CheminParam.number('userId'), CheminParam.optionalConst('edit'));


Test wether an object is a Chemin or not

Accepts one argument and return true if it's a Chemin, false otherwise.

Chemin.isChemin(Chemin.parse('/admin')); // true


An array of the parts (other Chemins or CheminParams) that make the chemin.

Note: You probably don't need this.

Note 2: You should not mutate this array or any of it's elements !

chemin.serialize(params?, options?)

Serialize a chemin

Accepts some params (an object or null) and an optional option object.

The option object accepts two boolean properties:

  • leadingSlash (default true): Add a slash at the begining
  • trailingSlash (default: false): Add a slash at the end
const chemin = Chemin.create('admin', CheminParam.number('userId'), CheminParam.optionalConst('edit'));
chemin.serialize({ userId: 42, edit: true }); // /admin/42/edit


Test a chemin against a pathanme

Accepts a pathname and return false or CheminMatchResult.

  • pathname can be either a string (/admin/user/5) or an array of strings (['admin', 'user', '5'])
  • CheminMatchResult is an object with two properties
    • rest: an array of string of the remaining parts of the pathname once the matching is done
    • params: an object of params extracted from the matching

Note: If you want to pass an array to pathname make sure to use CheminUtils.splitPathname.


Accepts the same arguments as chemin.match but return false if the path does not match or if rest is not empty, otherwise it returns the params object directly.


Return an array of all the Chemin it contains (as well as the Chemin itself).

import { Chemin } from 'chemin';

const admin = Chemin.create('admin');
const adminUser = Chemin.create(admin, 'user');

adminUser.extract(); // [adminUser, admin];


Return a string representation of the chemin.

import { Chemin, CheminParam as P } from 'chemin';

const postFragment = Chemin.create('post', P.number('postId'));
const postAdmin = Chemin.create('admin', P.string('userId'), postFragment, 'edit');

console.log(postAdmin.toString()); // /admin/:userId/post/:postId(number)/edit


Split a pathname and prevent empty parts

Accepts a string and returns an array od strings.

CheminUtils.splitPathname('/admin/user/5'); // ['admin', 'user', '5']


The CheminParam object contains the build-in CheminParam.


A number using parseFloat(x)

const chemin = Chemin.create(CheminParam.number('myNum'));
Chemin.matchExact(chemin, '/3.1415'); // { myNum: 3.1415 }


A integer using parseInt(x, 10)

const chemin = Chemin.create(CheminParam.integer('myInt'));
Chemin.matchExact(chemin, '/42'); // { myInt: 42 }


Any non-empty string

const chemin = Chemin.create(CheminParam.string('myStr'));
Chemin.matchExact(chemin, '/cat'); // { myStr: 'cat' }


A constant string

const chemin = Chemin.create(CheminParam.constant('edit'));
Chemin.matchExact(chemin, '/edit'); // {}
Chemin.matchExact(chemin, '/'); // false


Make any CheminParam optional

const chemin = Chemin.create(CheminParam.optional(CheminParam.integer('myInt')));
Chemin.matchExact(chemin, '/42'); // { myInt: { present: true, value: 42 } }
Chemin.matchExact(chemin, '/'); // { myInt: { present: false } }

CheminParam.optionalConst(name, path?)

An optional contant string

const chemin = Chemin.create(CheminParam.optionalConst('isEditing', 'edit'));
Chemin.matchExact(chemin, '/edit'); // { isEditing: true }
Chemin.matchExact(chemin, '/'); // { isEditing: false }

If path is omitted then the name is used as the path.

const chemin = Chemin.create(CheminParam.optionalConst('edit'));
Chemin.matchExact(chemin, '/edit'); // { edit: true }
Chemin.matchExact(chemin, '/'); // { edit: false }


An optional string parameter

const chemin = Chemin.create(CheminParam.optionalString('name'));
Chemin.matchExact(chemin, '/paul'); // { name: 'paul' }
Chemin.matchExact(chemin, '/'); // { name: false }

CheminParam.multiple(cheminParam, atLeastOne?)

Allow a params to be repeated any number of time

const chemin = Chemin.create(CheminParam.multiple(CheminParam.string('categories')));
Chemin.matchExact(chemin, '/'); // { categories: [] }
Chemin.matchExact(chemin, '/foo/bar'); // { categories: ['foo', 'bar'] }
const chemin = Chemin.create(CheminParam.multiple(CheminParam.string('categories'), true));
Chemin.matchExact(chemin, '/'); // false because atLeastOne is true
Chemin.matchExact(chemin, '/foo/bar'); // { categories: ['foo', 'bar'] }