I am trying to set up my node server / REST api.

For this i have a few different files:

division_model.js:

    module.exports = function(express, sequelize)

{

    var router = express.Router();

    router.route('/division');

    var DataTypes = require(sequelize);







    var Division = sequelize.define('division', {

            id: DataTypes.INTEGER,

            organization_id: DataTypes.INTEGER,

            location_id: DataTypes.INTEGER,

            name: DataTypes.STRING,

            parent_id: DataTypes.INTEGER



        }, {    freezeTableName: true,

            instanceMethods: {

                retrieveAll: function (onSuccess, onError) {

                    Division.findAll({}, {raw: true})

                        .ok(onSuccess).error(onError);

                },

                retrieveById: function (user_id, onSuccess, onError) {

                    Division.find({where: {id: user_id}}, {raw: true})

                        .success(onSuccess).error(onError);

                },

                add: function (onSuccess, onError) {

                    var username = this.username;

                    var password = this.password;



                    var shasum = crypto.createHash('sha1');

                    shasum.update(password);

                    password = shasum.digest('hex');



                    Division.build({username: username, password: password})

                        .save().ok(onSuccess).error(onError);

                },

                updateById: function (user_id, onSuccess, onError) {

                    var id = user_id;

                    var username = this.username;

                    var password = this.password;



                    var shasum = crypto.createHash('sha1');

                    shasum.update(password);

                    password = shasum.digest('hex');



                    Division.update({username: username, password: password}, {where: {id: id}})

                        .success(onSuccess).error(onError);

                },

                removeById: function (user_id, onSuccess, onError) {

                    Division.destroy({where: {id: user_id}}).success(onSuccess).error(onError);

                }

            }

        }

    );



// on routes that end in /users/:user_id

// ----------------------------------------------------

    router.route('/division/:division_id')



// update a user (accessed at PUT http://localhost:8080/api/users/:user_id)

        .put(function (req, res) {

            var user = User.build();



            Division.username = req.body.username;

            Division.password = req.body.password;



            Division.updateById(req.params.division_id, function (success) {

                console.log(success);

                if (success) {

                    res.json({message: 'User updated!'});

                } else {

                    res.send(401, User not found);

                }

            }, function (error) {

                res.send(User not found);

            });

        })



// get a user by id(accessed at GET http://localhost:8080/api/users/:user_id)

        .get(function (req, res) {

            var Division = Division.build();



            Division.retrieveById(req.params.division_id, function (users) {

                if (users) {

                    res.json(users);

                } else {

                    res.status(401).send(User not found);

                }

            }, function (error) {

                res.send(User not found);

            });

        })



// delete a user by id (accessed at DELETE http://localhost:8080/api/users/:user_id)

        .delete(function (req, res) {

            var division = Division.build();



            division.removeById(req.params.division_id, function (users) {

                if (users) {

                    res.json({message: 'User removed!'});

                } else {

                    res.status(401).send(User not found);

                }

            }, function (error) {

                res.send(User not found);

            });

        });

};

And my server.js

    // BASE SETUP

// =============================================================================

var express = require('express'),

    bodyParser = require('body-parser');

var app = express();

var router = express.Router();

var es = require('express-sequelize');

// =============================================================================



// IMPORT MODELS

// =============================================================================

app.use(bodyParser.json());

app.use(bodyParser.urlencoded({

    extended: true

}));

var env = app.get('env') == 'development' ? 'dev' : app.get('env');

var port = process.env.PORT || 8080;



var Sequelize = require('sequelize');



// db config

var env = dev;

var config = require('./database.json')[env];

var password = config.password ? config.password : null;



// initialize database connection

var sequelize = new Sequelize(

    config.database,

    config.user,

    config.password,

    {

        logging: console.log,

        define: {

            timestamps: false

        }

    }

);

//================================================================================



var division_model = require('./Divisions/division_model')(express,sequelize, router);



app.use('/division', division_model);



// REGISTER ROUTES

// =============================================================================

app.use('/api', app.router);



// START THE SERVER

// =============================================================================

app.listen(port);

console.log('Magic happens on port ' + port);

However with this i get the following error message when starting the server:

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

            ^

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

    at Function.<anonymous> (/var/www/example/backend/node_modules/express/lib/router/index.js:446:13)

    at Array.forEach (native)

    at Function.use (/var/www/example/backend/node_modules/express/lib/router/index.js:444:13)

    at EventEmitter.<anonymous> (/var/www/example/backend/node_modules/express/lib/application.js:187:21)

    at Array.forEach (native)

    at EventEmitter.use (/var/www/example/backend/node_modules/express/lib/application.js:184:7)

    at Object.<anonymous> (/var/www/example/backend/server.js:42:5)

    at Module._compile (module.js:456:26)

    at Object.Module._extensions..js (module.js:474:10)

    at Module.load (module.js:356:32)

Can anyone tell me why this is happening?