I am new to MEAN stack, so i am going through tutorials and it pretty clear that not all people use same logic.
But now i am stuck on these two examples

Example One

// server.js

var express = require('express'),

    app = express(),

    port = 1337;

// indicating view folder

app.set('views', './views');

// indicating view engine

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

// adding routes

require('./routes/index.js')(app);

require('./routes/user.js')(app);

//

app.listen(port);

module.exports = app;





./routes/index.js

module.exports = function(app) {

    // show indix view

    app.get('/', function(req, res) {

            res.render('index', {

                title: 'Index page',

            });

    });

};

above we are using get method from app (which is instance of express)

./routes/user.js

module.exports = function(app) {

    // showing user page

    app.route('/users').get(function(req, res) {

            res.render('user', {

                title: 'User page'

            });

    });

};

above we are using route method of express and then bind get to it

so when the app is running, and i access localhost:1337 index page is called
and when localhost:1337/user is called user page is called

Example two
Now when we use express myapp command, this example has some different logic

we have main app.js

var express = require('express');



var routes = require('./routes/index');

var users = require('./routes/users');



var app = express();



// view engine setup

app.set('views', path.join(__dirname, 'views'));

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



app.use('/', routes);

app.use('/users', users);



app.listen(1337);



module.exports = app;

As you can see first we require index and user route files required
and then we use app.use command to set routes.

in ./routes/index.js file

var express = require('express');

var router = express.Router();



/* GET home page. */

router.get('/', function(req, res, next) {

  res.render('index', { title: 'Express' });

});



module.exports = router;

we get method router of express and then bind get method to it

so my question is, when i commit app.use('/', routes); and call localhost:1337 i get error
but we have already using router in ./routes/index.js to show index page.
this should work according to first example.

EDIT error msg

Error: Not Found

    at app.use.res.render.message (/home/vagrant/meanstack/myapp/app.js:30:15)

    at Layer.handle [as handle_request] (/home/vagrant/meanstack/myapp/node_modules/express/lib/router/layer.js:82:5)

    at trim_prefix (/home/vagrant/meanstack/myapp/node_modules/express/lib/router/index.js:302:13)

    at /home/vagrant/meanstack/myapp/node_modules/express/lib/router/index.js:270:7

    at Function.proto.process_params (/home/vagrant/meanstack/myapp/node_modules/express/lib/router/index.js:321:12)

    at next (/home/vagrant/meanstack/myapp/node_modules/express/lib/router/index.js:261:10)

    at SendStream.error (/home/vagrant/meanstack/myapp/node_modules/express/node_modules/serve-static/index.js:107:7)

    at SendStream.emit (events.js:95:17)

    at SendStream.error (/home/vagrant/meanstack/myapp/node_modules/express/node_modules/send/index.js:244:17)

    at SendStream.onStatError (/home/vagrant/meanstack/myapp/node_modules/express/node_modules/send/index.js:340:48)

i had this code to handle error

app.use(function(req, res, next) {

    var err = new Error('Not Found');

    err.status = 404;

    next(err);

})

now when i comment this code and comment app.use('/', routes); and run the server.js

i get this when i run localhost:1337

Cannot GET / 

if you still cannot see the error, try express app in folder and create a new file server.js and add below code and run node server.js

var express = require('express');

var path = require('path');

var routes = require('./routes/index');

var users = require('./routes/users');



var app = express();



// view engine setup

app.set('views', path.join(__dirname, 'views'));

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



//app.use('/', routes);

app.use('/users', users);



app.listen(1337);



module.exports = app;

console.log( call 192.168.33.33:1337);