NodeJS Introduction

 NodeJS Introduction

  §  In this tutorial we will discuss NodeJS will help you learn the essentials of Node.js starting from the basics to an advanced level.

Prerequisites

  §  Before proceeding with this tutorial, you should have a Basic knowledge of HTML, JavaScript and web application is recommended.

WEB APPLICATION REQUIREMENTS :
ü Browser software.

ü Technology to develop client side.

ü Technology to develop server side.

ü User software.

ü Database software.

     WEB Server Software :

  §  Web server software is special piece of s/w (or) special s/w which can manages the web applications and web resources we executes this web resources automatically or dynamically whenever your requesting .

Responsibilities of web server :

§  It accepts all client http requests.

§  After accepting the request it passes your request to appropriate web resources of web application.

§  Web server proceeds your request and produce result.

§  Finally it will Gives resultant out put back to the client.

 

 What is NodeJS?

§  NodeJS is the Server side scripting language.

§  By using NodeJS, we can develop Http Servers.

§  We can develop Node application by using JavaScript.

§  Node follows Event Driven Model.

§  Node supports the modules. Predefined modules & custom modules.

 Features of NodeJS

§  NodeJS uses an event driven programming paradigm.

§  Event driving paradigm means that if we do any work, we need to raise an event for that work.

§  In this type of, flow of execution is determined by the events like user clicks or other programming threads or query result from database.

§  Events are handled by event handlers or event callbacks.

§  Event callback is nothing it is a function that is invoked when something significant happens like when click event is performed by user or the result of database query is available.

§  Non-blocking I/O model

§  When we send a request to the server and have to fetch some data, what we do is first our request goes to the server, and then the server sends the request database, searches its expected results and then gives it back to you again.

§  When the second request comes, the server accepts it, processes it and then gives a response. During this time, if two to three requests come at the same time, first it checks request on the priority basis that the request which come first that request serves first until first request has not been completed till second request has to wait.ie. The request will remain pending in queue. Once first request gives the result then second request process.

§  When we are sending a request in php/java/.net technology to the server Remaining request is blocked until the first request gets the result (second, third). This request remains blocked until the result of the first request is not gets.

 What happened when you send a request in NodeJS

§  Whenever we send a request in NodeJS. NodeJS listen the first request and after listing the first request NodeJS becomes ready to listing another request at the same time i.e. NodeJS  does not wait for I/O completion of the first request.

§  A NodeJS uses non-blocking I/O operations. This allows a single process to serve multiple requests at the same time. Instead of process being blocked and waiting for single I/O operation to complete, this waiting time is used to serve other requests. All Node.js libraries and the Node core api offer non-blocking operations with few minor exceptions.

  What difference between NodeJs and other server side web technology just

 like(Java/PHP/.Net)

Java |PHP |.Net

§  Browser Sends request to server.

§  Server sends request to database or file.

§  While the database or file is being read/written, the server simply waits until the operation is completed.

§  After completion of database/file operation, the content is sent to the browser.

§  The server is ready to receive next request.

NodeJS

§  Browser Sends request to server.

§  Server sends request to database or file.

§  Server will not wait until the completion of database operation/file operation simply   it receives another request starts its processing.

§  After completion of database/file operation, the content is sent to the browser.

 

 

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