app.js

var process = require('process');
var express = require('express');
var handlebars = require('express-handlebars');
var handlebarsSections = require('express-handlebars-sections');
var mongoose = require('mongoose');
var bodyParser = require('body-parser');
var app = express();

var models = require('./models');
 
var hbs = handlebars.create({defaultLayout: 'main', partialsDir: ['views/partials/']});
handlebarsSections(hbs);
app.engine('handlebars', hbs.engine);
app.set('view engine', 'handlebars');

app.use(bodyParser.urlencoded({ extended: true }));
app.use(bodyParser.json());
 
// connect to mongodb
mongoose.Promise = global.Promise;
mongoose.connect(process.env.MONGODB_URI, {useMongoClient: true}); 

function wantsJson() {
  return this.accepts('html', 'json') === 'json';
}

function smartRender(req, res, err, data, view) {
if (err)
  return res.send(err);

  if(req.wantsJson())
    return res.json(data);
  else
    return res.render(view, data);
}

app.use(function (req, res, next) {
  req.wantsJson = wantsJson;
  res.smartRender= smartRender;
  next();
});

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

app.listen(process.env.PORT || 3000)