koa-router

What is koa-router?

koa-router is a powerful routing middleware for Koa, a next-generation web framework for Node.js. It allows you to define routes for your web application, handle HTTP methods, and manage middleware in a clean and organized manner.

What are koa-router's main functionalities?

Basic Routing

This code demonstrates how to set up a basic route using koa-router. When a GET request is made to the root URL '/', it 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. When a GET request is made to '/users/:id', it responds with the user ID provided in the URL.

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. The logger middleware logs the HTTP method and URL of each request before passing control to the next middleware or route handler.

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 create nested routes with koa-router. The nestedRouter handles requests to '/nested/info' and responds with 'Nested Route Info'.

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

express

Express is a fast, unopinionated, minimalist web framework for Node.js. It provides robust routing capabilities similar to koa-router but is more widely used and has a larger ecosystem of middleware and plugins.

hapi

Hapi is a rich framework for building applications and services. It provides powerful configuration-based routing and extensive support for building scalable and maintainable applications. Compared to koa-router, Hapi offers more built-in features and a more opinionated structure.

restify

Restify is a framework specifically designed for building RESTful web services. It provides a similar routing mechanism to koa-router but is optimized for building APIs with a focus on performance and scalability.

README

koa-router

Router middleware for koa

• Express-style routing using app.get, app.put, app.post, etc.
• Named URL parameters and regexp captures.
• String or regular expression route matching.
• 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.

Installation

Install using npm:

npm install koa-router

API Reference

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

Router ⏏

Kind: Exported class

new Router([app], [opts])

Create a new router.

Param	Type	Description
[app]	koa.Application	extend koa app with router methods
[opts]	Object
[opts.prefix]	String	prefix router paths

Example
Basic usage:

var app = require('koa')();
var router = require('koa-router')();

router.get('/', function *(next) {...});

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

Or if you prefer to extend the app with router methods:

var app = require('koa')();
var router = require('koa-router');

app
  .use(router(app))
  .get('/', function *(next) {...});

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

Create router.verb() methods, where verb is one of the HTTP verbes 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().

router
  .get('/', function *(next) {
    this.body = 'Hello World!';
  })
  .post('/users', function *(next) {
    // ...
  })
  .put('/users/:id', function *(next) {
    // ...
  })
  .del('/users/:id', function *(next) {
    // ...
  });

Route paths will be translated to regular expressions used to match requests.

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', function *(next) {
 // ...
});

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

Multiple middleware

Multiple middleware may be given and are composed using koa-compose:

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

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.

Named parameters

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

Parameter middleware

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

router
  .param('user', function *(id, next) {
    this.user = users[id];
    if (!this.user) return this.status = 404;
    yield next;
  })
  .get('/users/:user', function *(next) {
    this.body = this.user;
  })

Regular expressions

Control route matching exactly by specifying a regular expression instead of a path string when creating the route. For example, it might be useful to match date formats for a blog, such as /blog/2013-09-04:

router.get(/^\/blog\/\d{4}-\d{2}-\d{2}\/?$/i, function *(next) {
  // ...
});

Capture groups from regular expression routes are added to ctx.captures, which is an array.

Kind: instance property of Router

Param	Type	Description
path	String | RegExp
[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(middleware, [...]) ⇒ Router

Use given middleware(s) before route callback. Only runs if any route is matched.

Kind: instance method of Router

Param	Type
middleware	function
[...]	function

Example

router.use(session(), authorize());

// runs session and authorize middleware before routing
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.

router.allowedMethods() is automatically mounted if the router is created with app.use(router(app)). Create the router separately if you do not want to use .allowedMethods(), or if you are using multiple routers.

Kind: instance method of Router

Param	Type	Description
[options]	Object
[options.throw]	Boolean	throw error instead of setting status and header

Example

var app = koa();
var router = router();

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

router.all(name, path, [middleware], callback) ⇒ Router

Register route with all methods.

Kind: instance method of Router

Param	Type	Description
name	String	Optional.
path	String | RegExp
[middleware]	function	You may also pass multiple middleware.
callback	function

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', function *() {
  this.redirect('/sign-in');
  this.status = 301;
});

Kind: instance method of Router

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

router.register(name, path, methods, middleware) ⇒ Route

Create and register a route.

Kind: instance method of Router

Param	Type	Description
name	String	Optional.
path	String | RegExp	Path string or regular expression.
methods	Array.<String>	Array of HTTP verbs.
middleware	function	Multiple middleware also accepted.

router.route(name) ⇒ Route | false

Lookup route with given name.

Kind: instance method of Router

Param	Type
name	String

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

Generate URL for route. Takes either map of named params or series of arguments (for regular expression routes).

router.get('user', '/users/:id', function *(next) {
 // ...
});

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

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

Kind: instance method of Router

Param	Type	Description
name	String	route name
params	Object	url parameters

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', function *(id, next) {
    this.user = users[id];
    if (!this.user) return this.status = 404;
    yield next;
  })
  .get('/users/:user', function *(next) {
    this.body = this.user;
  })

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 alexmingoia/koa-router repository!

Tests

Run tests using npm test.

Support

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

Changelog

4.3.2

• Do not send 405 if route matched but status is 404. Fixes #112, closes #114.