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

Question

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?

Answer 1

You must return a router in your middleware here:

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

So, your module export function should end with:

return router;

You also have conflicting ideas when setting this up. If you want the app to define the route as /division which you do here:

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

then you do not need to redefine the route again like you do here:

var router = express.Router();
router.route('/division');

You can simply:

app.use(division_model);

-- or --

/**
 * division_model.js
 */
var router = express.Router();
router.route('/');
//omitting route code
router.route('/:division_id');
//omitting route code

return router;

/**
 * server.js
 */

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

Answer 2

because you are exporting module with a function inside so you need to return your router at the end of your function at division_model.js

return router;

this should work