Beginning Guide to Node.Js Programming Language

What is Node.js?
Here are few thing you need to know about Node.Js

(1) Node.js is a server-side platform built on Google Chrome's JavaScript Engine (V8 Engine). Node.js was developed by Ryan Dahl in 2009 and its latest version is v0.10.36. The definition of Node.js as supplied by its official documentation is as follows −

  (2)  Node.js is a platform built on google Chrome's JavaScript runtime for easily building fast and scalable network applications. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across a good number of distributed devices.

(3) Node.js is an open source, cross-platform runtime environment for developing server-side and networking applications. Node.js applications are written in JavaScript, and can be run within the Node.js runtime on OS X, Microsoft Windows, and Linux.

(4) Node.js also provides a rich library of various JavaScript modules which simplifies the development of web applications using Node.js to a great extent.

Node.js = Runtime Environment + JavaScript Library

Features of Node.js
Below are the features which makes node.js suitable for software architects

  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 the MIT license.

Who Uses Node.js?

Following is the link on github wiki containing an exhaustive list of projects, application and companies which are using Node.js. This list includes eBay, General Electric, GoDaddy, Microsoft, PayPal, Uber, Wikipins, Yahoo!, and Yammer to name a few.

    Projects, Applications, and Companies Use Node

Node.js Concepts

Where to Use Node.js?

Following are the areas where Node.js is proving itself as a perfect technology partner.

 1   I/O bound Applications

  2  Data Streaming Applications

  3  Data Intensive Real-time Applications (DIRT)

  4  JSON APIs based Applications

5    Single Page Applications

Where Not to Use Node.js?

It is not advisable to use Node.js for CPU intensive applications.

    You really do not need to set up your own environment to start learning Node.js. Reason is very simple, we already have set up Node.js environment online, so that you can execute all the available examples online at the same time when you are doing your theory work. This gives you confidence in what you are reading and to check the result with different options. Feel free to modify any example and execute it online.

    Try following example using Try it option available at the top right corner of the below sample code box:

    /* Hello World! program in Node.js */
    console.log("Hello World!");

    For most of the examples given in this tutorial, you will find Try it option, so just make use of it and enjoy your learning.

Local Environment Setup

If you are interested in setting up  your environment for Node.js, you need the following two software available on your computer, (a) Text Editor and (b) The Node.js binary installer.
Text Editor

This will be used to type your program. Examples of few editors include Windows Notepad, OS Edit command, Brief, Epsilon, EMACS, and vim or vi.

Name and version of text editor can vary on different operating systems. For example, Notepad will be used on Windows, and vim or vi can be used on windows as well as Linux or UNIX.

The files you create with your editor are called source files and contain program source code. The source files for Node.js programs are typically named with the extension ".js".

Before starting your programming, make sure you have one text editor in place and you have enough experience to write a computer program, save it in a file, and finally execute it.
The Node.js Runtime

The source code written in source file is simply javascript. The Node.js interpreter will be used to interpret and execute your javascript code.

Node.js distribution comes as a binary installable for SunOS , Linux, Mac OS X, and Windows operating systems with the 32-bit (386) and 64-bit (amd64) x86 processor architectures.

Following section guides you on how to install Node.js binary distribution on various OS.
Download Node.js archive

Download latest version of Node.js installable archive file from Node.js Downloads. At the time of writing this tutorial, following are the versions available on different OS.
OS    Archive name
Windows    node-v6.3.1-x64.msi
Linux    node-v6.3.1-linux-x86.tar.gz
Mac    node-v6.3.1-darwin-x86.tar.gz
SunOS    node-v6.3.1-sunos-x86.tar.gz
Installation on UNIX/Linux/Mac OS X, and SunOS

Based on your OS architecture, download and extract the archive node-v6.3.1-osname.tar.gz into /tmp, and then finally move extracted files into /usr/local/nodejs directory. For example:

$ cd /tmp
$ wget
$ tar xvfz node-v6.3.1-linux-x64.tar.gz
$ mkdir -p /usr/local/nodejs
$ mv node-v6.3.1-linux-x64/* /usr/local/nodejs

Add /usr/local/nodejs/bin to the PATH environment variable.
OS    Output
Linux    export PATH=$PATH:/usr/local/nodejs/bin
Mac    export PATH=$PATH:/usr/local/nodejs/bin
FreeBSD    export PATH=$PATH:/usr/local/nodejs/bin
Installation on Windows

Use the MSI file and follow the prompts to install the Node.js. By default, the installer uses the Node.js distribution in C:\Program Files\nodejs. The installer should set the C:\Program Files\nodejs\bin directory in window's PATH environment variable. Restart any open command prompts for the change to take effect.
Verify installation: Executing a File

Create a js file named main.js on your machine (Windows or Linux) having the following code.

/* Hello, World! program in node.js */
console.log("Hello, World!")

Now execute main.js file using Node.js interpreter to see the result:

$ node main.js

If everything is fine with your installation, this should produce the following result:

Hello, World!

Before creating an actual "Hello, World!" application using Node.js, let us see the components of a Node.js application. A Node.js application consists of the following three important components −

    Import required modules − We use the require directive to load Node.js modules.

    Create server − A server which will listen to client's requests similar to Apache HTTP Server.

    Read request and return response − The server created in an earlier step will read the HTTP request made by the client which can be a browser or a console and return the response.

Creating Node.js Application
Step 1 - Import Required Module

We use the require directive to load the http module and store the returned HTTP instance into an http variable as follows −

var http = require("http");

Step 2 - Create Server

We use the created http instance and call http.createServer() method to create a server instance and then we bind it at port 8081 using the listen method associated with the server instance. Pass it a function with parameters request and response. Write the sample implementation to always return "Hello World".

http.createServer(function (request, response) {
   // Send the HTTP header
   // HTTP Status: 200 : OK
   // Content Type: text/plain
   response.writeHead(200, {'Content-Type': 'text/plain'});
   // Send the response body as "Hello World"
   response.end('Hello World\n');

// Console will print the message
console.log('Server running at');

The above code is enough to create an HTTP server which listens, i.e., waits for a request over 8081 port on the local machine.
Step 3 - Testing Request & Response

Let's put step 1 and 2 together in a file called main.js and start our HTTP server as shown below −

var http = require("http");

http.createServer(function (request, response) {

   // Send the HTTP header
   // HTTP Status: 200 : OK
   // Content Type: text/plain
   response.writeHead(200, {'Content-Type': 'text/plain'});
   // Send the response body as "Hello World"
   response.end('Hello World\n');

// Console will print the message
console.log('Server running at');

Now execute the main.js to start the server as follows

$ node main.js

Verify the Output. Server has started.
Beginning Guide to Node.Js Programming Language Beginning Guide to Node.Js Programming Language Reviewed by Joseph Chikeleze on May 11, 2018 Rating: 5

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