Encapsulate Express Routers - node.js

Question

Is it possible to create different routers using Express.Router that don't share middleware?
To me it seems that Express.Router uses a singleton, so no matter what I try, the middleware gets attached to all routers. So, without having to create multiple instances of the Express app, is there a way to achieve the following:
Create mutliple routers
var router_a = Express.Router();
var router_b = Express.Router();
Give each router unique routes and middleware
router_a.use(function(req, res, next){
console.log('Only works on router_a!');
});
router_a.get('/', function(req, res){
console.log('Only works on router_a!');
});
router_b.use(function(req, res, next){
console.log('Only works on router_b!');
});
router_b.get('/', function(req, res){
console.log('Only works on router_b!');
});
Attach each route to a custom url namespace
app.use('/a', router_a);
app.use('/b', router_b);
Is there a straight forward way to achieve this? After reading through the docs on the Router I don't see anything that suggests such is possible.

Answer 1

The one thing I see missing from your code is the call the next() in your middleware. If I add that to your code, it works perfectly fine for me.
The /b middleware is only called if the route starts with /b and same for the /a middleware with /a routes. And, to finish your code, you also have to send a response in your .get() handlers.
Here's the specific code I just tested:
var express = require('express');
var app = express();
var server = app.listen(80);
app.use(express.static('public'));
var router_a = express.Router();
var router_b = express.Router();
router_a.use(function(req, res, next){
console.log('.use() - Only works on router_a!');
next();
});
router_a.get('/', function(req, res){
console.log('.get() - Only works on router_a!');
res.send("router a, / route");
});
router_b.use(function(req, res, next){
console.log('.use() - Only works on router_b!');
next();
});
router_b.get('/', function(req, res){
console.log('.get() - Only works on router_b!');
res.send("router b, / route");
});
app.use('/a', router_a);
app.use('/b', router_b);