Introduction to Node.JS

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Presentation By Ramananda M.S Rao

ContentContentOverviewWhy NodeJSEnvironment SetupNode.js Console or virtual command line environment REPL Node Package ManagerGlobal vs. local package installationThe package.json configuration file or Node ConfigurationUnderstanding CPS (Continuation Passing Style)Automating tasks with GulpCommand Line InterfaceNode Process ModelSynchronous functionCall back FunctionEvent LoopNode Event LoopCreating a projectUtilitiesBuffersEvent EmittersTimersTimers and Scheduling

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ContentLow level File SystemsNode Model SystemNode Programming ModelHTTP communicationStreamsBinary DataCode ExecutionSystem Management ( Forks, Spawns and the Process )Network ProgrammingTCPDatagramsChild processTLS /SSLHTTPSAuthenticationWeb Sockets APISocket IO and IO.jsJSONConnecting to DatabasesThe Real-Time Web Express framework

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Overview and Features 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 distributed devices.

Node.js is an open source command line tool built for the server side JavaScript code.

The JavaScript is executed by the V8, a JavaScript engine developed by Google which is used in Chrome browser. It uses a JavaScript API to access the network and file system.

With Node.js it is as simple as doing it in client-side JavaScript code. It can be easily used to create concurrent server applications. The package manager for Node.js is npm and it works very well. In many

ways it resembles package managers from other ecosystems, but npm is fast, robust, and consistent. It does a great job specifying and installing project dependencies. It keeps packages isolated from other projects, avoiding version conflicts. But it also handles global installs of shell commands and platform-dependent binaries.

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Node.js First ApplicationCreating Node.js ApplicationStep 1: import required http moduleStep 2: create an server using http Create Server method.Step3: Pass a port 8081 to listen method.Step4: Create a js file named TestServer.jsStep5: Now run TestServer.js to see the resultStep 6: Verify the Output, Server has startedStep 7: Make a request to Node.js serverStep 8: Open http://127.0.0.1:8081/ on browser to see result.

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Node.js First Application// TestServer.jsmy_http = require("http");my_http.createServer(function(request,response){console.log("I got kicked");response.writeHeader(200, {"Content-Type": "text/plain"});response.end("Hello World");}).listen(8081);console.log("Server Running on 8081");

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Node.JS- NPMNPM (Node Package Manager) is included in Node.js installation since Node version 0.6.0., so there is no need to install it separately

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Node.js Process Model

Node.js Process Model:In this section, we will learn about the Node.js process model and understand why we should use Node.js.Traditional Web Server Model: 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.traditional web server model

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Node.js Process ModelNode.js Process Model: 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.

The following figure illustrates asynchronous web server model using Node.js.

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