TypeError: Router.use() requires middleware function but got a Object

There have been some middleware changes on the new version of express and I have made some changes in my code around some of the other posts on this issue but I can’t get anything to stick.

We had it working before hand but I can’t remember what the change was.

throw new TypeError('Router.use() requires middleware function but got a
        ^
TypeError: Router.use() requires middleware function but got a Object

node ./bin/www

js-bson: Failed to load c++ bson extension, using pure JS version
js-bson: Failed to load c++ bson extension, using pure JS version

/Users/datis/Documents/bb-dashboard/node_modules/express/lib/router/index.js:438
      throw new TypeError('Router.use() requires middleware function but got a
            ^
TypeError: Router.use() requires middleware function but got a Object
    at /Users/datis/Documents/bb-dashboard/node_modules/express/lib/router/index.js:438:13
    at Array.forEach (native)
    at Function.use (/Users/datis/Documents/bb-dashboard/node_modules/express/lib/router/index.js:436:13)
    at /Users/datis/Documents/bb-dashboard/node_modules/express/lib/application.js:188:21
    at Array.forEach (native)
    at Function.use (/Users/datis/Documents/bb-dashboard/node_modules/express/lib/application.js:185:7)
    at Object.<anonymous> (/Users/datis/Documents/bb-dashboard/app.js:46:5)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)

app.js

var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var mongoose = require('mongoose');
var session = require('express-session');
var MongoClient = require('mongodb').MongoClient;
var routes = require('./routes/index');
var users = require('./routes/users');

var Users = require('./models/user');
var Items = require('./models/item');
var Store = require('./models/store');
var StoreItem = require('./models/storeitem');

var app = express();
//set mongo db connection
var db = mongoose.connection; 

MongoClient.connect("mongodb://localhost:27017/test", function(err, db) {
  if(!err) {
    console.log("We are connected");
  }
});
// var MONGOHQ_URL="mongodb://localhost:27017/test" 

// view engine setup
app.set('views', path.join(__dirname, 'views'));

app.set('view engine', 'ejs');

// uncomment after placing your favicon in /public
//app.use(favicon(__dirname + '/public/favicon.ico'));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(session({
    secret: 'something',
    resave: true,
    saveUninitialized: true
}));

app.use('/', routes);
app.use('/users', users);
app.use(express.static(path.join(__dirname, 'public')));

// catch 404 and forward to error handler
// app.use(function(req, res, next) {
//     var err = new Error('Not Found');
//     err.status = 404;
//     next(err);
// });

// Make our db accessible to our router
app.use(function(req, res, next){
  req.db = db;
  next();
});

// error handlers

// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
    app.use(function(err, req, res, next) {
        res.status(err.status || 500);
        res.render('error', {
            message: err.message,
            error: err
        });
    });
}

// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
    res.status(err.status || 500);
    res.render('error', {
        message: err.message,
        error: {}
    });
});


module.exports = app;

It appears the answer to this question has changed for versioning reasons. Thanks to Nik

Answer

If your are using express above 2.x, you have to declare app.router like below code. Please try to replace your code

app.use('/', routes);

with

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

Please click here to get more details about app.router

Note:

app.router is depreciated in express 3.0+. If you are using express 3.0+, refer to Anirudh’s answer below.

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Answer

Note: