Pro JavaScript Techniques, Second Edition完整原版文件VIP专享VIP免费

uponthemake,model,andversionofbrowservisitingsaidprogrammer’swebsite.Bythemid-2000s,thebrowserwarsofthe90shadbeeneasilywonbyInternetExplorer,andbrowserdevelopmentstagnated.Twobrowserschallengedthisstateofaffairs:MozillaFirefoxandGoogleChrome.FirefoxwasthedescendantofNetscape,oneoftheearliestwebbrowsers.ChromehadGoogle’sbacking,morethanenoughtomakeitaninstantplayeronthescene.ButbothofthesebrowsersmadeafewdesigndecisionsthatfacilitatedtheJavaScriptrevolution.ThefirstdecisionwastosupporttheWorldWideWebconsortium’simplementationofvariousstandards.WhetherdealingwiththeDOM,eventhandling,orAjax,ChromeandFirefoxgenerallyfollowedthespecandimplementeditaswellaspossible.Forprogrammers,thismeantthatwedidn’thavetowriteseparatecodeforFirefoxandChrome.WewerealreadyusedtowritingseparatecodeforIEandsomethingelse,sohavingbranchingcodeinitselfwasnotnew.Butmakingsurethatthebranchingwasnotoverlycomplexwasawelcomerelief.Speakingofstandards,FirefoxandChromealsoputinalotofworkwiththeEuropeanComputerManufacturer’sAssociation(ECMA,nowstyledEcma).EcmaisthestandardsbodythatoverseesJavaScript.(Tobetechnical,EcmaoverseestheECMAScriptstandard,sinceJavaScriptisatrademarkofOracleand…well,wedon’treallycareaboutthosedetails,dowe?WewilluseJavaScripttorefertothelanguageandECMAScripttorefertothespecificationtowhichaJavaScriptimplementationadheres.)ECMAScriptstandardshadlanguishedinmuchthesamewayasIEdevelopment.Withtheriseofrealbrowsercompetition,theECMAScriptstandardwastakenupagain.ECMAScriptversion5(2009)codifiedmanyofthechangesthathadbeenmadeinthetenyears(!)sincethepreviousversionofthestandard.Thegroupitselfwasalsoenergized,withversion5.1comingoutin2011.Thefutureisprovidedfor,withsignificantworkcurrentlybeingdoneonbothversions6and7ofthestandard.Togivecreditwherecreditisdue,ChromepushedtheupdatingofJavaScriptaswell.TheChromeJavaScriptengine,calledV8,wasaveryimportantpartofChrome’sdebutin2008.TheChrometeambuiltanenginethatwasmuchfasterthanmostJavaScriptengines,andithaskeptthatgoalatthetopofthelistforsubsequentversions.Infact,theV8enginewassoimpressivethatitbecamethecoreofNode.js,abrowser-independentJavaScriptinterpreter.OriginallyintendedasaserverthatwoulduseJavaScriptasitsmainapplicationlanguage,NodehasbecomeaflexibleplatformforrunninganynumberofJavaScript-basedapplications.BacktoChrome:theothermajorinnovationGoogleintroducedtothelandofbrowserswastheconceptoftheevergreenapplication.Insteadofhavingtodownloadaseparatebrowserinstallforupdates,Chrome’sdefaultistoautomaticallyupdatethebrowserforyou.Whilethisapproachissometimesapaininthecorporateworld,itisagreatboontothenoncorporateconsumersurfer(alsoknownasaperson!).IfyouuseChrome(and,forthelastfewyears,Firefox),yourbrowserisup-to-date,withoutyourhavingtomakeanyeffort.WhileMicrosofthasdonethisforalongtimeinpushingsecurityupdatesviaWindowsUpdate,itdoesnotintroducenewfeaturestoInternetExplorerunlesstheyarecoupledtoanewversionofWindows.Toputitanotherway,updatestoIEareslowincoming.ChromeandFirefoxalwayshavethelatestandgreatestfeatures,aswellasbeingquitesecure.AsGooglepressedonwithChrome’sfeatures,theotherbrowsermakersplayedcatch-up.Sometimesthiscameinsillierways,suchaswhenFirefoxadaptedChrome’sversionnumbering.ButitalsoresultedinMozillaandMicrosofttakingacold,hardlookatJavaScriptengines.BothbrowsermakershavesignificantlyoverhauledtheirJSenginesoverthelas...