Let us learn Node.js – Part -1

What is Node.Js

Node.js is an open-source server side runtime environment built on Chrome’s V8 JavaScript engine. It provides an event driven, non-blocking (asynchronous) I/O and cross-platform runtime environment( on OS X, Microsoft Windows, and Linux) for building highly scalable server-side applications using JavaScript.

Node.js can be used to build different types of applications such as command line application, web application, real-time chat application, REST API server etc. However, it is mainly used to build network programs like web servers, similar to PHP, Java, or ASP.NET.

Why Node.js?

• Asynchronous and Event Driven − All APIs of Node.js library are asynchronous, that is, non-blocking. It essentially means a Node.js based server never waits for an API to return data. The server moves to the next API after calling it and a notification mechanism of Events of Node.js helps the server to get a response from the previous API call.
• Very Fast − Being built on Google Chrome’s V8 JavaScript Engine, Node.js library is very fast in code execution.
• Single Threaded but Highly Scalable − Node.js uses a single threaded model with event looping. Event mechanism helps the server to respond in a non-blocking way and makes the server highly scalable as opposed to traditional servers which create limited threads to handle requests. Node.js uses a single threaded program and the same program can provide service to a much larger number of requests than traditional servers like Apache HTTP Server.
• No Buffering − Node.js applications never buffer any data. These applications simply output the data in chunks.
• License − Node.js is released under theMIT licence

Few users who use node.js : eBay, General Electric, GoDaddy, Microsoft, PayPal, Uber, Wikipins, Yahoo!, and Yammer to name a few.

What is non-blocking?

In the traditional web server model, each request is handled by a dedicated thread from the thread pool. If no thread is available in the thread pool at any point of time then the request waits till the next available thread. Dedicated thread executes a particular request and does not return to thread pool until it completes the execution and returns a response.

Node.js processes user requests differently when compared to a traditional web server model. Node.js runs in a single process and the application code runs in a single thread and thereby needs less resources than other platforms. All the user requests to your web application will be handled by a single thread and all the I/O work or long running job is performed asynchronously for a particular request. So, this single thread doesn’t have to wait for the request to complete and is free to handle the next request. When asynchronous I/O work completes then it processes the request further and sends the response.

An event loop is constantly watching for the events to be raised for an asynchronous job and executing callback function when the job completes. Internally, Node.js uses libev for the event loop which in turn uses internal C++ thread pool to provide asynchronous I/O.

Where to use Node.js

• I/O bound Applications
• Data Streaming Applications
• Data Intensive Real-time Applications (DIRT)
• JSON APIs based Applications
• Single Page Applications

Setting up Node.js

Download two softwares to get started 1. node 2. texteditor

Install node.js from https://nodejs.org

download respective os version, and verify installation by running command node -V

first program in Node.js

Copy the below one line Code in text editor and save it as myFirstnodeprogram.js

console.log("Hello World");

Run the program , from command prompt

node myFirstnodeprogram.js

In Next part, we shall learn , simple server program.