In Official Blog, Programming
It’s absolutely no doubt that JavaScript is ruling the web world.JavaScript’s rising popularity has brought with it a lot of changes, and the face of web development today is dramatically different. The things that we can do on the web nowadays with JavaScript running on the server, as well as in the browser, were hard to imagine.
As official website states: “Node.js® is a JavaScript runtime built on Chrome’s V8 JavaScript engine. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient.” In simple words we can say that this technology runs JavaScript on server side.
Node.js was introduced late in 2009 by Ryan Dahl at a JavaScript conference with an idea to enrich the server side with the power of JavaScript. Back in past most of the real time web application are created by using client server architecture. In such architecture we have to use two different languages for client side and server side scripting for example we use php as a server side language and JavaScript for scripting in client side.
But node.js removes this conflict, Now we can write real time as well as complex web applications in just one language using node.js. This will definitely removes the overhead of bridging both languages and debugging them individually.
Node.JS owes its incredible speed and performance to a technique called the event loop and The fact that it runs on top of V8, the JavaScript interpreter and virtual machine that Google Created to make their Chrome web browser run impossibly fast
Installing Node
Node.js is very easy to install. If you’re using Windows or Mac, installers are available on the download page.
Installing on windows
On Windows, go to http://nodejs.org and download the MSI installer. Every release of node has a corresponding MSI installer that you need to download and execute. The filename follows the format nodev?.?.?.msi. Upon 
executing it, simply follow the instructions in the setup wizard shown in fig
To ensure that the installation worked, open the shell or command prompt by running cmd.exe and typing
node –version.
The version name of the package you just installed should display.
Installed Node. What Next?
Once installed you’ll have access to a new command called “node”. Now Open the node command and run this command to check if it’s working
node –version
You can see it simply output your node version on screen
You can use the node command in two different ways. The first is with no arguments. This will open an interactive shell (REPL: read-eval-print-loop) where you can execute raw JavaScript code. The other way to run Node is by providing it a JavaScript file to execute. This is almost always how you’ll be using it.
To open REPL simply type node on command prompt the cursor will now come in next line with a “ > ” sign here you can write and evaluate JavaScript code if you’re a beginner with javascript you can test your expressions here. Type following to test environment
console.log(‘Hello World’);
Further you can try this
object.keys(global)
Secondly you can write your code on a js file and execute it with node command
Open Your favorite text editor and write these lines and save it first.js.
var http = require(‘http’);
var serv = http.createServer(function (req, res) {
res.writeHead(200, { ’Content-Type’: ’text/html’ });
res.end(’<marquee>Node Running Everywhere!</marquee>’);});
serv.listen(3000);
Run the file:
open shell or node command prompt and type
node first.js
In the above code snippet, you’re harnessing the power of Node to script a fully compliant HTTP server that serves a basic HTML document.
Node.js use asynchronous callbacks. Basically when you tell it to do something and when it’s done it will call your function (callback). This is because Node is single-threaded. While you’re waiting on the callback to fire, Node can go off and do other things instead of blocking until the request is finished.
This is especially important for web servers. It’s pretty common in modern web applications to access a databases. While you’re waiting for the database to return results Node can process more requests. This allows you to handle thousands of concurrent connections with very little overhead, compared to creating a separate thread for each connection.
Further we will discuss more about npm – the package manager for node.js and other powerful features of it.
