Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine. It allows JavaScript to be run on the server-side. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, especially for data-intensive real-time applications that run across distributed devices. It has a large and active community that supports it with packages for building all sorts of server-side applications and web services.

1. NODE JS
Server Side JavaScript

2. Background
• V8 is an open Source JavaScript engine developed my google ,it is used in google chrome browser
• Node Js runs onV8
• It is Open Source and created in 2009

3. Why Node ?
“Node's goal is to provide an easy way to build scalable Network programs”
• Non Blocking I/O model
• It makes use of event loops via JavaScript’s callback functionality
• Windows, Linux, Mac
• 1 Language for Frontend and Backend
• Easy to get started.

4. Event Loop

5. Non Blocking
• Blocking
• Non-Blocking

6. Queued Inputs
• If you’re receiving a high amount of concurrent data, your database can become a bottleneck.
• But because database access is a blocking operation (in this case), we run into trouble.
• The solution is to acknowledge the client’s behavior before the data is truly written to the database

7. Node JS Modules
• Node js heavily relies on modules
• Creating an in -built module is easy, just put JS code in a separate js file and include in the code b
using require
Var module_cal = require(‘./calculator’);
• Libraries in Node js are called packages and they can be installed by typing
npm install “package_name”
• NPM (Node Package Manager ) Comes bundled with Node js installation

8. Node JS Modules
• Express -to make syntax and DB connections simpler
• Nodemon - to monitor Node.js and push change automatically
• Mongoskin - to make mongo queries simpler

9. myfirstmodule.js:
app.js:
Browser:
Node JS Modules:Examples

10. Example:Hello World !

11. What can be done with Node JS
• Create HTTP/TCP Server
• Create DNS Server
• Static File Server
• Web Chat Application
• Games or anything which sends updates to user in real-time