@koa/router

What is @koa/router?

@koa/router is a powerful and flexible routing library for Koa, a popular web framework for Node.js. It allows developers to define routes and handle HTTP requests with ease, providing a clean and modular way to build web applications and APIs.

What are @koa/router's main functionalities?

Basic Routing

This code demonstrates how to set up a basic route using @koa/router. It creates a Koa application, defines a router, and sets up a GET route for the root URL that responds with 'Hello World!'.

const Koa = require('koa');
const Router = require('@koa/router');

const app = new Koa();
const router = new Router();

router.get('/', (ctx, next) => {
  ctx.body = 'Hello World!';
});

app.use(router.routes());
app.use(router.allowedMethods());

app.listen(3000);

Route Parameters

This code demonstrates how to use route parameters with @koa/router. It sets up a route that captures a user ID from the URL and responds with the user ID.

const Koa = require('koa');
const Router = require('@koa/router');

const app = new Koa();
const router = new Router();

router.get('/users/:id', (ctx, next) => {
  const userId = ctx.params.id;
  ctx.body = `User ID: ${userId}`;
});

app.use(router.routes());
app.use(router.allowedMethods());

app.listen(3000);

Middleware

This code demonstrates how to use middleware with @koa/router. It defines a logger middleware that logs the HTTP method and URL of each request, and applies it to a route.

const Koa = require('koa');
const Router = require('@koa/router');

const app = new Koa();
const router = new Router();

const logger = async (ctx, next) => {
  console.log(`${ctx.method} ${ctx.url}`);
  await next();
};

router.get('/', logger, (ctx, next) => {
  ctx.body = 'Hello World!';
});

app.use(router.routes());
app.use(router.allowedMethods());

app.listen(3000);

Nested Routes

This code demonstrates how to set up nested routes with @koa/router. It creates a nested router and mounts it under a parent route.

const Koa = require('koa');
const Router = require('@koa/router');

const app = new Koa();
const router = new Router();
const nestedRouter = new Router();

nestedRouter.get('/info', (ctx, next) => {
  ctx.body = 'Nested Route Info';
});

router.use('/nested', nestedRouter.routes(), nestedRouter.allowedMethods());

app.use(router.routes());
app.use(router.allowedMethods());

app.listen(3000);

Other packages similar to @koa/router

koa-router

koa-router is another popular routing library for Koa. It provides similar functionality to @koa/router, including support for route parameters, middleware, and nested routes. However, @koa/router is a more modern and actively maintained fork of koa-router.

express

Express is a widely-used web framework for Node.js that includes built-in routing capabilities. While it is not specifically designed for Koa, it offers similar routing features and is known for its simplicity and flexibility. Developers who prefer a more comprehensive framework might choose Express over Koa and @koa/router.

hapi

Hapi is a rich framework for building applications and services in Node.js. It includes a powerful routing system that supports route parameters, middleware, and nested routes. Hapi is known for its configuration-driven approach and extensive plugin ecosystem, making it a strong alternative to Koa and @koa/router.

README

koa-router

Call for Mantainers

This module if fork from koa-router, the most widely used router module in koa community, because of it is lake of activity now. Thanks for the greate work of @alexmingoia and the original team.

And now we need maintainers for this project. Anyone interested can creates pull requests to fixes bugs or implements new features, we will add active contributors as collaborators.

Router middleware for koa

• Express-style routing using app.get, app.put, app.post, etc.
• Named URL parameters.
• Named routes with URL generation.
• Responds to OPTIONS requests with allowed methods.
• Support for 405 Method Not Allowed and 501 Not Implemented.
• Multiple route middleware.
• Multiple routers.
• Nestable routers.
• ES7 async/await support.

Migrating to 7 / Koa 2

• The API has changed to match the new promise-based middleware signature of koa 2. See the koa 2.x readme for more information.
• Middleware is now always run in the order declared by .use() (or .get(), etc.), which matches Express 4 API.

Installation

Install using npm:

npm install @koa/router

API Reference

• koa-router
  • Router ⏏
    • new Router([opts])
    • instance
      • .get|put|post|patch|delete|del ⇒ Router
      • .routes ⇒ function
      • .use([path], middleware) ⇒ Router
      • .prefix(prefix) ⇒ Router
      • .allowedMethods([options]) ⇒ function
      • .redirect(source, destination, [code]) ⇒ Router
      • .route(name) ⇒ Layer | false
      • .url(name, params, [options]) ⇒ String | Error
      • .param(param, middleware) ⇒ Router
    • static
      • .url(path, params) ⇒ String

Router ⏏

Kind: Exported class

new Router([opts])

Create a new router.

Param	Type	Description
[opts]	Object
[opts.prefix]	String	prefix router paths

Example
Basic usage:

var Koa = require('koa');
var Router = require('koa-router');

var app = new Koa();
var router = new Router();

router.get('/', (ctx, next) => {
  // ctx.router available
});

app
  .use(router.routes())
  .use(router.allowedMethods());

router.get|put|post|patch|delete|del ⇒ Router

Create router.verb() methods, where verb is one of the HTTP verbs such as router.get() or router.post().

Match URL patterns to callback functions or controller actions using router.verb(), where verb is one of the HTTP verbs such as router.get() or router.post().

Additionaly, router.all() can be used to match against all methods.

router
  .get('/', (ctx, next) => {
    ctx.body = 'Hello World!';
  })
  .post('/users', (ctx, next) => {
    // ...
  })
  .put('/users/:id', (ctx, next) => {
    // ...
  })
  .del('/users/:id', (ctx, next) => {
    // ...
  })
  .all('/users/:id', (ctx, next) => {
    // ...
  });

When a route is matched, its path is available at ctx._matchedRoute and if named, the name is available at ctx._matchedRouteName

Route paths will be translated to regular expressions using path-to-regexp.

Query strings will not be considered when matching requests.

Named routes

Routes can optionally have names. This allows generation of URLs and easy renaming of URLs during development.

router.get('user', '/users/:id', (ctx, next) => {
 // ...
});

router.url('user', 3);
// => "/users/3"

Multiple middleware

Multiple middleware may be given:

router.get(
  '/users/:id',
  (ctx, next) => {
    return User.findOne(ctx.params.id).then(function(user) {
      ctx.user = user;
      next();
    });
  },
  ctx => {
    console.log(ctx.user);
    // => { id: 17, name: "Alex" }
  }
);

Nested routers

Nesting routers is supported:

var forums = new Router();
var posts = new Router();

posts.get('/', (ctx, next) => {...});
posts.get('/:pid', (ctx, next) => {...});
forums.use('/forums/:fid/posts', posts.routes(), posts.allowedMethods());

// responds to "/forums/123/posts" and "/forums/123/posts/123"
app.use(forums.routes());

Router prefixes

Route paths can be prefixed at the router level:

var router = new Router({
  prefix: '/users'
});

router.get('/', ...); // responds to "/users"
router.get('/:id', ...); // responds to "/users/:id"

URL parameters

Named route parameters are captured and added to ctx.params.

router.get('/:category/:title', (ctx, next) => {
  console.log(ctx.params);
  // => { category: 'programming', title: 'how-to-node' }
});

The path-to-regexp module is used to convert paths to regular expressions.

Kind: instance property of Router

Param	Type	Description
path	String
[middleware]	function	route middleware(s)
callback	function	route callback

router.routes ⇒ function

Returns router middleware which dispatches a route matching the request.

Kind: instance property of Router

router.use([path], middleware) ⇒ Router

Use given middleware.

Middleware run in the order they are defined by .use(). They are invoked sequentially, requests start at the first middleware and work their way "down" the middleware stack.

Kind: instance method of Router

Param	Type
[path]	String
middleware	function
[...]	function

Example

// session middleware will run before authorize
router
  .use(session())
  .use(authorize());

// use middleware only with given path
router.use('/users', userAuth());

// or with an array of paths
router.use(['/users', '/admin'], userAuth());

app.use(router.routes());

router.prefix(prefix) ⇒ Router

Set the path prefix for a Router instance that was already initialized.

Kind: instance method of Router

Param	Type
prefix	String

Example

router.prefix('/things/:thing_id')

router.allowedMethods([options]) ⇒ function

Returns separate middleware for responding to OPTIONS requests with an Allow header containing the allowed methods, as well as responding with 405 Method Not Allowed and 501 Not Implemented as appropriate.

Kind: instance method of Router

Param	Type	Description
[options]	Object
[options.throw]	Boolean	throw error instead of setting status and header
[options.notImplemented]	function	throw the returned value in place of the default NotImplemented error
[options.methodNotAllowed]	function	throw the returned value in place of the default MethodNotAllowed error

Example

var Koa = require('koa');
var Router = require('koa-router');

var app = new Koa();
var router = new Router();

app.use(router.routes());
app.use(router.allowedMethods());

Example with Boom

var Koa = require('koa');
var Router = require('koa-router');
var Boom = require('boom');

var app = new Koa();
var router = new Router();

app.use(router.routes());
app.use(router.allowedMethods({
  throw: true,
  notImplemented: () => new Boom.notImplemented(),
  methodNotAllowed: () => new Boom.methodNotAllowed()
}));

router.redirect(source, destination, [code]) ⇒ Router

Redirect source to destination URL with optional 30x status code.

Both source and destination can be route names.

router.redirect('/login', 'sign-in');

This is equivalent to:

router.all('/login', ctx => {
  ctx.redirect('/sign-in');
  ctx.status = 301;
});

Kind: instance method of Router

Param	Type	Description
source	String	URL or route name.
destination	String	URL or route name.
[code]	Number	HTTP status code (default: 301).

router.route(name) ⇒ Layer | false

Lookup route with given name.

Kind: instance method of Router

Param	Type
name	String

router.url(name, params, [options]) ⇒ String | Error

Generate URL for route. Takes a route name and map of named params.

Kind: instance method of Router

Param	Type	Description
name	String	route name
params	Object	url parameters
[options]	Object	options parameter
[options.query]	Object | String	query options

Example

router.get('user', '/users/:id', (ctx, next) => {
  // ...
});

router.url('user', 3);
// => "/users/3"

router.url('user', { id: 3 });
// => "/users/3"

router.use((ctx, next) => {
  // redirect to named route
  ctx.redirect(ctx.router.url('sign-in'));
})

router.url('user', { id: 3 }, { query: { limit: 1 } });
// => "/users/3?limit=1"

router.url('user', { id: 3 }, { query: "limit=1" });
// => "/users/3?limit=1"

router.param(param, middleware) ⇒ Router

Run middleware for named route parameters. Useful for auto-loading or validation.

Kind: instance method of Router

Param	Type
param	String
middleware	function

Example

router
  .param('user', (id, ctx, next) => {
    ctx.user = users[id];
    if (!ctx.user) return ctx.status = 404;
    return next();
  })
  .get('/users/:user', ctx => {
    ctx.body = ctx.user;
  })
  .get('/users/:user/friends', ctx => {
    return ctx.user.getFriends().then(function(friends) {
      ctx.body = friends;
    });
  })
  // /users/3 => {"id": 3, "name": "Alex"}
  // /users/3/friends => [{"id": 4, "name": "TJ"}]

Router.url(path, params) ⇒ String

Generate URL from url pattern and given params.

Kind: static method of Router

Param	Type	Description
path	String	url pattern
params	Object	url parameters

Example

var url = Router.url('/users/:id', {id: 1});
// => "/users/1"

Contributing

Please submit all issues and pull requests to the koajs/koa-router repository!

Tests

Run tests using npm test.

Support

If you have any problem or suggestion please open an issue here.

Changelog

8.0.0 / 2019-06-16

others

• b5dd5e8] - chore: rename to @koa/router (dead-horse)

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Changelogs inherit from koa-router.