[Learning.Node(Early.Release,2012.6)].Shelley.Powers.文字版

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1、PrefaceNotYourOrdinaryJavaScriptYoupickedtheperfecttimetolearnNode.ThetechnologyevolvingaroundNodeisstillyoungandvibrant,withinterestingnewvariationsandtwistspoppinguponaregularbasis.Atthesametime,thetechnologyhasreachedalevelofmaturitythatassuresyouyourti

2、melearningNodewillbewellspent:installationhasneverbeeneasier,evenonWindows;the"bestofbreed"modulesarebeginningtosurfacefromtheseeminghundredsavailableforuse;theinfrastructureisbecomingrobustenoughforproductionuse.Twoimportantthingstokeepinmindwhenyouworkwi

3、thNode.ThefirstisthatitisbasedinJavaScript,moreorlessthesameJavaScriptyou'reusedtoworkingwithinclient-sidedevelopment.True,youcanuseanotherlanguagevariation,suchasCoffeeScript,butJavaScriptisthelinguafrancaofthetechnology.Thesecondimportantthingtorememberi

4、sthatNodeisn'tyourordinaryJavaScript.Thisisserver-sidetechnology,whichmeanssomeofthefunctionality—andsafeguards—you'vecometoexpectinyourbrowserenvironmentjustwon'tbethere,andallsortsofnewandpotentiallyveryunfamiliarcapabilities,will.wnloadfromWow!eBook

5、.wowebook.com>oOfcourse,ifNodewaslikeJavaScriptinthebrowser,whatfunwouldthatbe?DWhyNode?IfyouexplorethesourcecodeforNode,you'llfindthesourcecodeforGoogle'sV8,theJavaScript(technically,ECMAScript)enginethat'salsoatthecoreofGoogle'sChromebrowser.Oneadvantage

6、toNode.js,then,isthatyoucandevelopNodeapplicationsforjustoneimplementationofJavaScript—nothalfadozendifferentbrowsersandbrowserversions.Yes,nomoreworryingabouthavingtocodeJavaScriptforIE6.Well,atleastnotforNode.Nodeisdesignedtobeusedforapplicationsthatareh

7、eavyoninput/output,butlightoncomputation.Moreimportantly,itprovidesthisfunctionalitydirectlyoutofthebox.Youdon'thavetoworryaboutblockingwhilewaitingforafiletofinishloading,oradatabasetofinishupdating,becausemostofthefunctionalityisasynchronousbydefault.And

8、youdon'thavetoworryaboutworkingwiththreads,becauseNodeisimplementedonasinglethread.Mostimportantly,Nodeiswritteninalanguagethatmanytraditionalwebdevelopersarefamiliarwith:JavaScript.Youmaybelearninghowtousene