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Node js is said to be an open source. It is the cross-platform JavaScript runtime to developing different types of applications and tools.
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Tableof contents AboutNodejs EnvironmentSetup Firstapplication REPLTerminal Callbackconcept EventloopandEmitter BuffersandStreams GlobalobjectsandFilesystem Webmodule ExpressFramework
AboutNodejs Node.jssaidtobetherealJavaScriptbased platformandframeworkwhichismainlybuilton Googlechrome’sJavaScriptengine. Itutilizedtoexpandtheinputandoutput exhaustivewebapplicationslikewebapplications, singlepageapplications, andvideostreaming sites. Itissaidtobeanopensourceanditalso completelyfreewhichisusedbythemillionsof developeracrosstheglobe.
Environment Setup Theusersdon’tneedtogoovertheirsetuptostart learningthenode.js. Itisasimpleuserinterfacewherethenode.jshasthe environmenttolearnonline. Hereyoucanquicklyexecutewithmanyexamplesover theonlineatthesametimeduringyourtheorywork. Itgivesyoutheconfidencetocheckouttheresultwiththe differentnumberofoptions.
Firstapplication Firstofall, beforecreatingtheactualapplicationusing theNode.js, wehavetocheckoutthecomponentsof thenode.jsapplication. Threetypesofcomponents Importrequiredmodules Readrequestandreturnresponse Createserver
REPLTerminal REPLstandsfortheReadEvalPrintLoop. Itmainlyrepresentsthecomputerenvironmentsetuplike UNIXorLinuxandWindowsconsoleinaninteractivemode. NodeorNode.jscomestogetherwiththeREPL Environment. ItalsomainlyperformsthetaskssuchasRead, Print, EvalandLoop. MainfeaturesofREPLofanodeareveryhelpfulin experimentingtodebugJavaScriptcodesandnode.js.
CallbackConcept Thecallbackissaidtoasynchronousequivalentforthe function. Thefunctionofthecallbackismainlycalledasthe completionofthetask. thenodemakesgreatusageofthecallback. HerealltheAPIsofthenodeareprimarilywritteninaway whichsupportsthecallbacks. Thereforeoncetheinputandoutputfileiscomplete, then itwillcallthecallbackfunctionduringtheperiodof passingcallbackfunctionwiththecontentofthefileasa parameter. Fortheinformation, thatisthereisnoblocking orwaitfortheinputandoutputfile.
Event Loop Node.jsuseseventsheavilyanditisalsooneofthe reasonswhyNode.jsisprettyfastcomparedtoother similartechnologies. AssoonasNodestartsitsserver, itsimplyinitiatesits variables, declaresfunctionsandthensimplywaitsfor theeventtooccur. Inanevent-drivenapplication, thereisgenerallyamain loopthatlistensforevents, andthentriggersacallback functionwhenoneofthoseeventsisdetected.
Event Emitter ManyobjectsinaNodeemitevents. forexample, anet.Serveremitsaneventeachtimea peerconnectstoit, anfs.readStreamemitsanevent whenthefileisopened. Allobjectswhichemiteventsaretheinstancesof events.EventEmitter.
Buffers BufferissaidtobethepureJavaScriptwhichisaUnicode- friendly, anditisnotforbinarydata. Bufferclassisaglobalclassthatcanbeaccessedinan applicationwithoutimportingthebuffermodule. NodeprovidesBufferclasswhichprovidesinstancesto storerawdatasimilartoanarrayofintegersbut correspondstoarawmemoryallocationoutsidetheV8 heap.
Streams Streamsareobjectsthatletyoureaddatafromasourceor writedatatoadestinationincontinuousfashion. therearefourtypesofstreams Readable − Streamwhichisusedforreadoperation. Writable − Streamwhichisusedforwriteoperation. Duplex − Streamwhichcanbeusedforbothreadand writeoperation. Transform − Atypeofduplexstreamwheretheoutputis computedbasedoninput.
Global objects Itissaidtobeglobalinnature, andthatis mainlyavailableinallthemodules. Thustheuserdoesnotneedtheobjectsto includeinanyapplicationinsteadofusing themdirectly. Theobjectsarefunctions, modules, strings.
Filesystem Filesystemissaidtobethenodewhichmainly implementsthefileinputandoutputusingthe wrappersaroundPOSIXfunctions. Thusthenodefilesystemmoduleisimported byusingthesyntaxvarfs = require (“fs”). Theobjectsarefunctions, modules, strings.
Webmodule Thewebserveristhesoftwareapplicationwhichismainly handlingtheHTTPrequeststhataresentbytheHTTPclient webpagesandwebbrowserstotheclients. TheserversareusuallydeliveringtheHTMLdocumentswith scripts, sheets, style, andimages. Thereforemostofthesupporttheserversidescriptsand usingthescriptinglanguagesorbyredirectingtheprocess totheapplicationserverwhichmainlyhelpstoreceivethe datafromthedatabase.
Express Framework TheexpressissaidtobetheflexibleandminimalNode.js webapplicationframework. Itprovidestherobust numberoffeaturestoimprovethemobileapplications andtodeveloptheweb. Italsomainlyfacilitatesthecontinuousdevelopmentof webapplications.
FeaturesofExpress Framework ItallowsrenderingtheHTMLpageswhichismostly basedonthepassingargumentstotemplates. Italsodefinestheroutingtablethatisusedtocarryout thedifferentmovementswhicharebasedonURLand HTTPmethod. Itismainlyallowedtosetupthemiddleware’swhich helpstorespondtoHTTPrequests.
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