# Develop Express application

MVC is common architecture which many applications prefer. MVC stands for Model-View-Controller:

• Model - Implement the main features of the application, handling databases and so on.
• Controller - Dealing with requests, communicating with Models and Views.
• View - The UI layer of the application

So, we would like to choose this application development mode, and here is the basic structure of our folders:

- models/- controllers/- views/- app.js-package.json

And in this project, I also create a Service layer which take the responsibility to handling the data — so the Model layer just needs to define the Data objects.

## Routes

In the project, we could define routing rules in the Controllers, but it is better to declare the rules in separated files.

For some small projects, a single route file is enough. Because there would not be many routing rules in the project comparing to other codes.

However, it is a better practice to use multiple routing files as it will make your project’s structure clearer. Here is a example routing rules:

app.get('/', site.index);app.post('/register', user.register);

site and user are the names of two Controllers, defining different GET or POST rules.

## MongoDB

MongoDB is convenient for Node.js to manipulating for MongoDB is a document database which use JSON objects to store data. So it is quite simple to handle data with MongoDB using Node.js.

In the project, we would like to use Mongoose as our ORM for MongoDB. Below is an example of connecting MongoDB:

var mongoose = require('mongoose');mongoose.connect('mongodb://127.0.0.1/test',function(err){if(err){    console.log('connect to %s error: ', err.message);    process.exit(1);}});

And define a Scheme called User:

var mongoose = require('mongoose');varSchema= mongoose.Schema;varUserSchema=newSchema({  name:{ type:String},  password:{ type:String}});mongoose.model('User',UserSchema);