make express.Router() return a Router function instance

Similar to how express() returns an express `app` instance which is also
a function, express.Router() returns the Router instance which is also a
function and can be easily used via another router or the app.

app.use(express.Router());

lib/router/index.js

@@ -9,31 +9,32 @@ var Route = require('./route')
   , debug = require('debug')('express:router')
   , parseUrl = utils.parseUrl;
 
-/**
- * Expose `Router` constructor.
- */
-
-exports = module.exports = Router;
-
 /**
  * Initialize a new `Router` with the given `options`.
  *
  * @param {Object} options
- * @api private
+ * @return {Router} which is an callable function
+ * @api public
  */
 
-function Router(options) {
+var proto = module.exports = function(options) {
   options = options || {};
-  var self = this;
 
-  self.params = {};
-  self._params = [];
-  self.caseSensitive = options.caseSensitive;
-  self.strict = options.strict;
-  self.stack = [];
+  function router(req, res, next) {
+    router.handle(req, res, next);
+  };
 
-  self.middleware = self.handle.bind(self);
-}
+  // mixin Router class functions
+  router.__proto__ = proto;
+
+  router.params = {};
+  router._params = [];
+  router.caseSensitive = options.caseSensitive;
+  router.strict = options.strict;
+  router.stack = [];
+
+  return router;
+};
 
 /**
  * Map the given param placeholder `name`(s) to the given callback.
@@ -69,7 +70,7 @@ function Router(options) {
  * @api public
  */
 
-Router.prototype.param = function(name, fn){
+proto.param = function(name, fn){
   // param logic
   if ('function' == typeof name) {
     this._params.push(name);
@@ -107,7 +108,7 @@ Router.prototype.param = function(name, fn){
  * @api private
  */
 
-Router.prototype.handle = function(req, res, done) {
+proto.handle = function(req, res, done) {
   var self = this;
 
   debug('dispatching %s %s', req.method, req.url);
@@ -127,7 +128,7 @@ Router.prototype.handle = function(req, res, done) {
   var options = [];
 
   // middleware and routes
-  var stack = this.stack;
+  var stack = self.stack;
 
   // for options requests, respond with a default if nothing else responds
   if (method === 'options') {
@@ -242,7 +243,7 @@ Router.prototype.handle = function(req, res, done) {
  * @api private
  */
 
-Router.prototype.process_params = function(route, req, res, done) {
+proto.process_params = function(route, req, res, done) {
   var self = this;
   var params = this.params;
 
@@ -317,7 +318,7 @@ Router.prototype.process_params = function(route, req, res, done) {
  * @api public
  */
 
-Router.prototype.use = function(route, fn){
+proto.use = function(route, fn){
 
   // default route to '/'
   if ('string' != typeof route) {
@@ -356,7 +357,7 @@ Router.prototype.use = function(route, fn){
  * @api public
  */
 
-Router.prototype.route = function(path){
+proto.route = function(path){
   var route = new Route(path);
 
   var layer = Layer(path, {
@@ -381,7 +382,7 @@ Router.prototype.route = function(path){
  * @api public
  */
 
-Router.prototype.all = function(path, fn) {
+proto.all = function(path, fn) {
   var route = this.route(path);
   methods.forEach(function(method){
     route[method](fn);
@@ -390,9 +391,10 @@ Router.prototype.all = function(path, fn) {
 
 // create Router#VERB functions
 methods.forEach(function(method){
-  Router.prototype[method] = function(path, fn){
+  proto[method] = function(path, fn){
     var self = this;
     self.route(path)[method](fn);
     return self;
   };
 });
+

test/Router.js

@@ -6,7 +6,31 @@ var express = require('../')
 
 describe('Router', function(){
 
-  describe('.middleware', function(){
+  it('should return a function with router methods', function() {
+    var router = Router();
+    assert(typeof router == 'function');
+
+    var router = new Router();
+    assert(typeof router == 'function');
+
+    assert(typeof router.get == 'function');
+    assert(typeof router.handle == 'function');
+    assert(typeof router.use == 'function');
+  });
+
+  it('should support .use of other routers', function(done) {
+    var router = Router();
+    var another = Router();
+
+    another.get('/bar', function(req, res) {
+      res.done();
+    });
+    router.use('/foo', another);
+
+    router.handle({ url: '/foo/bar', method: 'GET' }, { done: done });
+  });
+
+  describe('.handle', function(){
     it('should dispatch', function(done){
       var router = new Router();
 

test/app.options.js

@@ -31,7 +31,7 @@ describe('OPTIONS', function(){
     var router = new express.Router();
 
     router.get('/users', function(req, res){});
-    app.use(router.middleware);
+    app.use(router);
     app.get('/other', function(req, res){});
 
     request(app)