Node.js is an open-source JavaScript runtime environment that allows for building server-side web applications. It uses the Google V8 JavaScript engine to interpret JavaScript code and an event-driven, non-blocking I/O model, making it lightweight and efficient. The document then discusses advantages of Node.js like using JavaScript on both the server and browser, reducing mismatches. It provides an example of creating a simple chat service using Node.js, Socket.io and JQuery and discusses important Socket.io functions like emitting and listening for data.

1. Node.js is an open-source, cross-platform
runtime environment for developing server-side
Web applications. The runtime environment
interprets JavaScript using Google's V8
JavaScript engine. Node.js uses an event-driven,
non-blocking I/O model that makes it
lightweight and efficient.

2. Advantages
 Web development in a dynamic language (JavaScript) on a
VM that is incredibly fast (V8). It is much faster than Ruby,
Python, or Perl.
 Ability to handle thousands of concurrent connections with
minimal overhead on a single process.
 Using JavaScript on a web server as well as the browser
reduces the impedance mismatch between the two
programming environments which can communicate data
structures via JSON that work the same on both sides of the
equation. Duplicate form validation code can be shared
between server and client, etc.

3. Creating a simple chat service
What We need:
NodeJS
Socket.io
JQuery

4. Socket.IO enables real-time bidirectional event-based
communication.
It works on every platform, browser or device, focusing
equally on reliability and speed.

5. Uses
Real-time analytics
 Push data to clients that gets represented as real-time
counters, charts or logs.
Instant messaging and chat
 Send data real-time to the client.
Binary streaming
 it's possible to send any blob back and forth: image, audio,
video.
Document collaboration
 Allow users to concurrently edit a document and see each
other's changes.

6. Important things to remember in Socket.io
that we will be using
Socket.emit(name, objectData)
Send data to the server
socket.emit(‘chat', { some: 'data' });
Socket.on(‘messages’, function(data) {})
Listen if there’s a data base on socket name

7. Data Process