API.md

API Reference

Index

• Router ⏏
  • new Router([opts])
  • router.get|put|post|patch|delete|del ⇒ Router
  • Named routes
  • Match host
  • Multiple middleware
• Nested routers
  • Router prefixes
  • URL parameters
  • router.routes ⇒ function
  • router.use([path], middleware) ⇒ Router
  • router.prefix(prefix) ⇒ Router
  • router.allowedMethods([options]) ⇒ function
  • router.redirect(source, destination, [code]) ⇒ Router
  • router.route(name) ⇒ Layer | false
  • router.url(name, params, [options]) ⇒ String | Error
  • router.param(param, middleware) ⇒ Router
  • Router.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
[opts.exclusive]	Boolean	only run last matched route's controller when there are multiple matches
[opts.host]	String/Regexp	hostname to match for all routes

Example Basic usage:

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

const app = new Koa();
const 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().

Additionally, 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"

Match host

Routers can match against a specific host by using the host property.

const routerA = new Router({
  host: 'hosta.com' // only match if request host exactly equal `hosta.com`
});

router.get('/', (ctx, next) => {
  // Response for hosta.com
});

const routerB = new Router({
  host: /^(.*\.)?hostb\.com$/ // match all subdomains of hostb.com, including hostb.com, www.hostb.com, etc.
});

router.get('/', (ctx, next) => {
  // Response index for matched hosts
});

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:

const forums = new Router();
const 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:

const 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, if and only if, a route is matched.

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

const router = new Router({
  prefix: '/categories'
});

router.get('/', ...); // respond "/categories"

router.prefix('/users');

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

Note: prefix always should start from / otherwise it won't work.

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

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

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

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

Example with Boom

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

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

app.use(router.routes());
app.use(router.allowedMethods({
  throw: true,
  notImplemented: () => Boom.notImplemented(),
  methodNotAllowed: () => 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. This method URL-encodes the parameters before including them in the URL.

Kind: static method of Router

Param	Type	Description
path	String	url pattern
params	Object	url parameters

Example

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