Node.js 101

What is Node.js?

Node.js is a server-side platform built on Google Chrome's JavaScript Engine (V8 Engine).

Where to use Node.js

I/O Bound Applications
JSON API Based Applications
Single Page Applications

Installing Node.js

From Binaries: Download the Node.js Binaries from Official Download Page Go To Downloads page
On Ubuntu:
curl -sL https://deb.nodesource.com/setup_6.x | sudo -E bash - sudo apt-get install -y nodejs

Creating a Simple Node.js Application

Initializing a Node.js Application

Make a New Folder for your Node.js Application and cd into that new folder using Terminal (CMD)

mkdir SampleNodeJSApp  
cd SampleNodeJSApp/

Initialize a Node.js Application using NPM package manager

npm init

Now you will be asked a series of questions. You need to answer according to your project.

name : Name of your project in lowercase
version : Version of your project.
description : Description about your Project
entry point : Defines entry point for App. Usually index.js or server.js
test command : Command to execute test suite
git repository : Link of Git repo
keywords : Keywords which describes your application best.
author : Your Name
license : License

Now you will be presented a generated package.json file to review.

Sample Directory Structure for Node.js App

assets : Contains all client-side assets that require compilation
css : Contains all your LESS/Stylus style-sheets
js : Contains your client-side CoffeeScript/ES6 files
dist : Contains all compiled server-side scripts
LICENSE : License file
package.json : file contains meta data about your app or module
public : Contains your static files that are not handled by any compilers
README.md : Read Me file
routes.js : Contains all routes
server.js : Entry Point
src : Contains all server-side scripts
controller : Contains all Controllers
middleware : Contains all middleware scripts
model : Contains Models if Mongoose is used
test : Contains all unit testing scripts ( implemented using a testing-framework of your choice )
views : Contains all your express views ( pug,handlebars, ejs or any other templating engine )

Some Frameworks Available for Node.js

Express.js : a minimalist framework for building a host of web and mobile applications as well as application programming interfaces (APIs).
Hapi.js : a powerful Node.js web framework for building application program interfaces (APIs) and other software applications.
Socket.io : a Node.js server framework for building real-time web applications
Meteor : an open-source, model-view controller (MVC) framework for building websites and web/mobile applications.
Sails.js : Sails.js is one of the most popular real-time frameworks around for building Node.js applications. Sails.js offers a model-view controller (MVC) pattern for implementing data-driven application programming interfaces (APIs).

Some of the Databases that can be used as our app's backend

MongoDB : a free and open-source cross-platform document-oriented database program
MYSQL : an open-source relational database management system (RDBMS).
PostgreSQL : an object-relational database (ORDBMS)

There are hundreds of NoSQL Databases available that can be integrated with Node.js. Finding one for your application type is your responsibility :p.

To Proceed with the sample app I'll choose Express.js and MongoDB
Installing Express.js

npm install express --save

--save option will add express to package.json
Assuming MongoDB installed on your system
If not follow this link
Installing MongoDB driver

npm install mongodb --save

We will be creating a simple user authentication system using passport.js
Add passport and passport-local dependencies to package.json

"passport": "~0.2.0",
"passport-local": "~1.0.0"

We need some other dependencies too.Finally your dependencies should look like this

"dependencies": {
        "bcrypt-nodejs": "latest",
        "body-parser": "^1.12.4",
        "connect-flash": "^0.1.1",
        "cookie-parser": "^1.3.5",
        "cookie-session": "^1.1.0",
        "crypto": "^0.0.3",
        "express": "^4.12.4",
        "express-handlebars": "^3.0.0",
        "express-validator": "^2.10.0",
        "mongodb": "^2.2.22",
        "mongoose": "^4.8.1",
        "morgan": "^1.7.0",
        "passport": "^0.2.2",
        "passport-local": "^1.0.0",
        "serve-static": "^1.9.3"
    }

Now we need to choose a templating engine for our Node.js app
Few Popular Choices will be

Handlebars
EJS
Pug
dust.js
Mustache.js

Personally I would go for Handlebars. Because it is similar to HTML. It is upto you to choose a Templating engine. I recommend you to go through each of these templating engines and choose one that suits you.
Or you can use AngularJS , ReactJS or Something like VueJS for the frontend
Some Additional Modules used in Sample Application

Mongoose : Mongoose provides a straight-forward, schema-based solution to model your application data.
Morgan : HTTP request logger middleware for node.js

Let's get down to Business
First we need to define a User model for our application using Mongoose. ( or not use Mongoose at all. Read more about this issue )

I have implemented only local registration part. you can refer passport.js website to know more about social media logins.
Now we can implement passport.js login and signup strategies
Routes will look like this
Our Application's Entry Point Server.js will look like this
Final Output
Final Folder Structure
You can find the source to this Sample Application Here

GITHUB REPOSITORY

Guide to setup

Fork this Repo Fork
Clone Forked Repo to your local machine

git clone https://github.com/YOURUSERNAME/Sample-Node.js-Application.git

Install dependencies

npm install

Start Application

npm start