OReilly AJAX hacks tips and tools for creating responsive websites mar 2006 ISBN 0596101694

AjaxHacks
ByBruceW.Perry
...............................................
Publisher:O'Reilly
PubDate:March2006
PrintISBN-10:0-596-10169-4
PrintISBN-13:978-0-59-610169-5
Pages:438

TableofContents|Index

Ajax,thepopulartermforAsynchronousJavaScriptandXML,isoneofthemostimportant
combinationsoftechnologiesforwebdeveloperstoknowthesedays.Withitsrich
groupingoftechnologies,Ajaxdeveloperscancreateinteractivewebapplicationswith
XML-basedwebservices,usingJavaScriptinthebrowsertoprocessthewebserver
response.
TakingcompleteadvantageofAjax,however,requiressomethingmorethanyourtypical
"how-to"book.WhatitcallsforisAjaxHacksfromO'Reilly.Thisvaluableguideprovides
direct,hands-onsolutionsthattakethemysteryoutofAjax'smanycapabilities.Eachhack
representsacleverwaytoaccomplishaspecifictask,savingyoucountlesshoursof
searchingfortherightanswer.
Asmartcollectionof100insidertipsandtricks,AjaxHackscoversallofthetechnology's
finerpoints.Wanttobuildnext-generationwebapplicationstoday?Thisbookcanshow
youhow.Amongthemultitudeoftopicsaddressed,itshowsyoutechniquesfor:
UsingAjaxwithGoogleMapsandYahooMaps
DisplayingWeather.comdata
Scrapingstockquotes
Fetchingpostalcodes
Buildingwebformswithauto-completefunctionality
AjaxHacksalsofeaturesanumberofadvancedhacksforacceleratedwebdevelopers.
Discoverhowtocreatehuge,maintainablebookmarklets,howtouseclient-sidestorage

forAjaxapplications,andhowtocallabuilt-inJavaobjectfromJavaScriptusingAjax.The
bookevenaddressesbestpracticesfortestingAjaxapplicationsandimproving
maintenance,performance,andreliabilityforJavaScriptcode.
ThelatestinO"Reilly'scelebratedHacksseries,AjaxHackssmartlycomplementsother


O'ReillytitlessuchasHeadRushAjaxandJavaScript:TheDefinitiveGuide.


AjaxHacks
ByBruceW.Perry
...............................................
Publisher:O'Reilly
PubDate:March2006
PrintISBN-10:0-596-10169-4
PrintISBN-13:978-0-59-610169-5
Pages:438

TableofContents|Index

Foreword
creditsCredits
AbouttheAuthor
Contributors
Acknowledgments
Preface
BuildingSingle-PageApplications
ExplainingAjax
HowtoUseThisBook
HowThisBookIsOrganized
ConventionsUsedinThisBook
UsingCodeExamples
SafariEnabled
HowtoContactUs
GotaHack?
Chapter1.AjaxBasics
It'sNotaFloorWax
HandlewithCare
XMLHttpRequest
Hack1.DetectBrowserCompatibilitywiththeRequestObject
Hack2.UsetheRequestObjecttoPOSTDatatotheServer
Hack3.UseYourOwnLibraryforXMLHttpRequest
Hack4.ReceiveDataasXML
Hack5.GetPlainOldStrings

Hack6.ReceiveDataasaNumber
Hack7.ReceiveDatainJSONFormat
Hack8.HandleRequestObjectErrors
Hack9.DigintotheHTTPResponse
Hack10.GenerateaStyledMessagewithaCSSFile
Hack11.GenerateaStyledUserMessageontheFly
Chapter2.WebForms
Hack12.SubmitTextFieldortextareaValuestotheServerWithoutaBrowser
Refresh
Hack13.DisplayTextFieldortextareaValuesUsingServerData
Hack14.SubmitSelection-ListValuestotheServerWithoutaRoundTrip
Hack15.DynamicallyGenerateaNewSelectionListUsingServerData
Hack16.ExtendanExistingSelectionList

Hack17.SubmitCheckboxValuestotheServerWithoutaRoundTrip
Hack18.DynamicallyGenerateaNewCheckboxGroupwithServerData
Hack19.PopulateanExistingCheckboxGroupfromtheServer
Hack20.ChangeUnorderedListsUsinganHTTPResponse
Hack21.SubmitHiddenTagValuestoaServerComponent
Chapter3.Validation
Hack22.ValidateaTextFieldortextareaforBlankFields
Hack23.ValidateEmailSyntax
Hack24.ValidateUniqueUsernames
Hack25.ValidateCreditCardNumbers
Hack26.ValidateCreditCardSecurityCodes
Hack27.ValidateaPostalCode
Chapter4.PowerHacksforWebDevelopers
Hack28.GetAccesstotheGoogleMapsAPI
Hack29.UsetheGoogleMapsAPIRequestObject
Hack30.UseAjaxwithaGoogleMapsandYahoo!MapsMash-up
Hack31.DisplayaWeather.comXMLDataFeed
Hack32.UseAjaxwithaYahoo!MapsandGeoURLMash-up
Hack33.DebugAjax-GeneratedTagsinFirefox
Hack34.FetchaPostalCode
Hack35.CreateLarge,MaintainableBookmarklets
Hack36.UsePermanentClient-SideStorageforAjaxApplications
Hack37.ControlBrowserHistorywithiframes
Hack38.SendCookieValuestoaServerProgram
Hack39.UseXMLHttpRequesttoScrapeanEnergyPricefromaWebPage
Hack40.SendanEmailwithXMLHttpRequest

Hack41.FindtheBrowser'sLocaleInformation
Hack42.CreateanRSSFeedReader
Chapter5.DirectWebRemoting(DWR)forJavaJocks
Hack43.IntegrateDWRintoYourJavaWebApplication
Hack44.UseDWRtoPopulateaSelectionListfromaJavaArray
Hack45.UseDWRtoCreateaSelectionListfromaJavaMap
Hack46.DisplaytheKeys/ValuesfromaJavaHashMaponaWebPage
Hack47.UseDWRtoPopulateanOrderedListfromaJavaArray
Hack48.AccessaCustomJavaObjectwithJavaScript
Hack49.CallaBuilt-inJavaObjectfromJavaScriptUsingDWR
Chapter6.HackAjaxwiththePrototypeandRicoLibraries
Hack50.UsePrototype'sAjaxToolswithYourApplication
Hack51.UpdateanHTMLElement'sContentfromtheServer
Hack52.CreateObserversforWebPageFields
Hack53.UseRicotoUpdateSeveralElementswithOneAjaxResponse
Hack54.CreateaDrag-and-DropBookstore
Chapter7.WorkwithAjaxandRubyonRails
SensibleMVC
Hack55.InstallRubyonRails

Hack56.MonitorRemoteCallswithRails
Hack57.MakeYourJavaScriptAvailabletoRailsApplications
Hack58.DynamicallyGenerateaSelectionListinaRailsTemplate
Hack59.FindOutWhetherAjaxIsCallingintheRequest
Hack60.DynamicallyGenerateaSelectionListUsingDatabaseData
Hack61.PeriodicallyMakeaRemoteCall
Hack62.DynamicallyViewRequestInformationforXMLHttpRequest
Chapter8.Savorthescript.aculo.usJavaScriptLibrary
Hack63.Integratescript.aculo.usVisualEffectswithanAjaxApplication
Hack64.CreateaLoginBoxThatShrugsOffInvalidLogins
Hack65.CreateanAuto-CompleteFieldwithscript.aculo.us
Hack66.CreateanIn-PlaceEditorField
Hack67.CreateaWebFormThatDisappearsWhenSubmitted
Chapter9.OptionsandEfficiencies
Hack68.FixtheBrowserBackButtoninAjaxApplications
Hack69.HandleBookmarksandBackButtonswithRSH
Hack70.SetaTimeLimitfortheHTTPRequest
Hack71.ImproveMaintainability,Performance,andReliabilityforLarge
JavaScriptApplications
Hack72.ObfuscateJavaScriptandAjaxCode

Hack73.UseaDynamicscriptTagtoMakeWebServicesRequests
Hack74.ConfigureApachetoDealwithCross-DomainIssues
Hack75.RunaSearchEngineInsideYourBrowser
Hack76.UseDeclarativeMarkupInsteadofScriptviaXForms
Hack77.BuildaClient-SideCache
Hack78.CreateanAuto-CompleteField
Hack79.DynamicallyDisplayMoreInformationAboutaTopic
Hack80.UseStringsandArraystoDynamicallyGenerateHTML
Index


Foreword
Thetruthis,I'veneverbuiltanAjaxapplication.
Sure,I'veworkedonAjaxprojects.Butwhenitcomesto
programming,myexperienceisprettylimited.I'vedonesome
JavaScriptinghereandthere.IknowalittlePerl,buthardly
enoughtobuildawebapplication.Asaprogrammer,I'mmore
ofanoccasionalweekendhobbyistthananythingelse.
Youcanimaginehowfrustratingitisforpeopletolearnthisfact
whentheysendmeemailsaskingforhelpwiththeirJavaScript.

Butyoucanhardlyfaultthemforexpectingmetobea
technologist.Afterall,Iwroteanarticlecoiningtheterm
"Ajax,"andAjaxisallabouttechnology,right?
ThefunnythingisthatIdidn'tseeitthatwaywhenIwas
writingtheessay.Ididn'tthinkIwaswritingfortechnologists
atall.I'madesigner,andIthoughtIwaswritingforadesign
audience.Ifyoulookatsomeoftheotherthingswe've
publishedonadaptivepath.com,youcanseethatwe'remuch
morelikelytobetalkingaboutwaystoanalyzeuserbehavioror
makeanexperienceconnectwithpeoplethanaboutthelatest
codelibrariesordataschemas.
That'sonereasonsomepeoplethoughtitwasalittlestrange
formetobewritingaboutAjaxatall.Designers,onewayof
thinkinggoes,shouldleavewritingabouttechnologyto
technologists.
ButseeingAjaxasapurelytechnologicalphenomenonmisses
thepoint.Ifanything,Ajaxisevenmoreofaseachangefor
designersthanitisfordevelopers.Sure,therearealotofways
inwhichdevelopersneedtochangetheirthinkingastheymake
thetransitionfrombuildingtraditionalwebapplicationsto
buildingAjaxapplications.Butforthoseofuswhodesignuser


experiences,thechangebroughtaboutbyAjaxisevenmore
profound.
We'vegottenprettygoodatourjobsinthelast10yearsorso.
We'vestartedtogetahandleonwhattheWebdoeswelland
whattheWebdoespoorly.Andwe'vedevelopedanarsenalof
conventionstorelyonwhenwedesignapplications:wherethe
logogoes,howalinkbehaveswhenitisclicked,howto

communicatethatsomethingevencanbeclicked...
Allofthatknowledgewell,mostofit,anywaygoesoutthe
windowwithAjax.Wehaveawiderpalettetoworkwith,but
thatalsomeanswehavemoreopportunitiestomakemistakes.
Andbelieveme,we'llmakealotofthem.Ittakestimetoget
smart,andjustasittookusawhiletogetahandleontheold
staticWeb,it'lltakeussometimetogetgoodatcreatingAjax
experiencesaswell.
Andthat'swhereyouandthisbookcomein.
OneofthemostinspiringthingsabouttheWebisthatanyone
cancontributetoitsdevelopment.Standardsbodiesand
platformvendorsareimportant,ofcourse,butthereisno
masterplanfortheevolutionoftheWeb.TheWebgoeswhere
itsuserswantittogobutonlywhenthey'reready.Sometimes
thatmeansagreatideadoesn'ttakeholdrightaway,and
sometimesthatmeansitonlytakesonevoicetobringthatidea
toanaudiencereadytohearit.
Allofus,designersanddeveloperstogether,arethearchitects
oftheWeb.Throughtoolslikethisbook,wecanlearnfrom
eachother,andwecanuseourcreativitytospuronfurther
innovation.Thechoiceswemakenowlaythegroundworkfor
whatistocome.Atthismoment,Ajaxisourmanifestdestiny,
theobviousnextchapterinthestoryoftheWeb.Whenthis
chapterisover,I'llbeexcitedtoseewhatthenextonebrings.
Butfornow,let'sseewhatwecandowithwhatwe'vegot.


Nowgetoutthere,andgethacking!
JesseJamesGarrett
SanFrancisco,CA

December2005




Credits
AbouttheAuthor
Contributors
Acknowledgments


AbouttheAuthor
BrucePerryisanindependentsoftwaredeveloperandwriter,
andtheauthorofO'Reilly'sJavaServlet&JSPCookbook.Since
1996,hehasdevelopedwebapplicationsanddatabasesfor
variousnonprofits,designandmarketingfirms,aswellas
publishers.Inhissparetime,Perryisanactiveage-group
triathleteandhascycledextensivelyintheSwissAlps.Helives
intheNewburyport,MassachusettsareawithhiswifeStacy
LeBaron,daughterRachel,andsonScott.




Contributors
MicahDubinkoservedasaneditorandauthorofthe
XForms1.0W3Cspecification,andhebeganparticipatingin
theXFormseffortinSeptember1999,ninemonthsbefore
theofficialWorkingGroupwaschartered.Micahreceivedan
InfoWorldInnovatorawardin2004.Heistheauthorof

O'Reilly'sXFormsEssentials,availableonlineat
.Currently,Micahworksfor
Yahoo!inCaliforniaasaseniorresearchdeveloper.
CurtHibbsisaseniorsoftwaredeveloperinSt.Louiswith
morethan30years'experienceinplatforms,languages,
andtechnologiestoonumeroustolist.Withakeen(and
alwayssearching)eyefornewmethodsandtechnologiesto
makehisworkeasierandmoreproductive,hehasbecome
veryactiveintheRubydevelopmentcommunity.
BradNeuberghasdoneextensiveworkintheopensource
community,contributingcodetoMozilla,JXTA,theJakarta
FeedParser,andmore.Hisexperienceincludesdeveloping
onWallStreetwithdistributedsystems,n-tierdesign,and
J2EE.AsseniorsoftwareengineeratRojoNetworks,Brad
focusedonnext-generationaggregators,theblogosphere,
MySQL,Ajax,andLucene.Recentworkincludesconsulting
fortheInternetArchivetocreateanAjaxbookreader;
focusingonAjax/DHTMLopensourceframeworks,including
theReallySimpleHistorylibraryrecentlyadoptedby
Google;andworkingwiththeAjaxMassiveStorageSystem
(AMASS)anddojo.storage,whichallowwebapplicationsto
permanentlyandsecurelystoremegabytesofdata.
PremshreePillaiisaTechnicalYahoo!.Hehacks(maintains
theRubyAPIsforYahoo!WebServices,Flickr,Technorati,


etc.),writes("RubyCorner,"acolumnforLinuxForYou),
andtalks(atvariousconferences)aboutRubyinhisfree
time.HehaspreviouslycontributedtoO'Reilly'sPython
CookbookandYahoo!Hacks,andtotheACM'sCrossroads.

MarkPruettisaprogrammerandwriterlivinginVirginia,
whereheworksforaFortune500energycompany.He's
theauthoroftwobooksandnumerousarticleson
programmingandtechnology.Markreceivedhismasterof
sciencedegreeincomputersciencefromVirginia
CommonwealthUniversity.
SeanSniderisaseniorwebsoftwareengineerforYahoo!
andtheWebUserInterfaceTeammanagerforYahoo!Music
Unlimited.SeanhasbeenbuildingAjaxapplicationsandrich
websitesforovereightyearswithinthemusic,videogame,
ande-commerceindustries,forcompaniessuchas
ElectronicArts(EASports,),
Musicmatch(MusicmatchJukebox,
),andiVillage.com.




Acknowledgments
Myfamilymembersplaythemostimportantroleingivinglife
toabookidea,nurturingitswriting,andmakingitsfinal
publicationpossible.First,IthankmyparentsAnneandRobert
Perry,whohadthewisdomtosettleinConcord,Massachusetts,
wherebooksarevaluedperhapsmorethaninanyothertownin
theUnitedStates.Theypromotedreadingduringmychildhood
asanactivityabovemostallothers,perhapssecondonlyto
gettingoutsideandappreciatingtheenvironmentandMother
Nature.
Second,IwouldliketothankmywifeStacyandchildrenRachel
andScott,whoexhibitedgreatpatiencewhiledealingwiththe

modestcrisesofpublicationdeadlines,suchasthetemporary
lossoftheirhusbandandfathertotheinnersanctorumofa
homeoffice,ortheoccasionalover-cookingofthepeasasI
racedbacktomylaptoptocompletesomeunfinished
paragraph.
I'dliketothankmyO'ReillyeditorSimonSt.Laurent,who
tirelesslysteeredthisbooktopublicationfrombeginningto
end,andofferedcogentadviceduringtheentiredurationof
writing,despitethechallengingtimeline.Thisbookgreatly
benefitedfromthetechnicalreviewsinitiatedbyMicahDubinko,
ShelleyPowers,ThinakornTabtieng,andMichaelBuffington.
Theydemonstratedimpressiveversatilityintakingbothalong
viewofthebook'stopic,aswellasfocusingonnumerousfinegraineddetailsthatrequiredcorrectionsorgreaterexposition.




Preface
Ajax,atermcoinedin2005todescribethecombinationofa
groupofpopularwebtechnologies,hasbeenaninstanthitin
thesoftwareworld.Instantsuccesscanraisemanydoubts,but
itwouldbeamistaketoviewthissoftwaremodelassimplythe
latest"nextbigthing"tomakeabigsplashandthenvanishinto
theetheroftheWeb.
Why?Firstofall,Ajax'sinterweavedtechnologies,including
JavaScript,theDocumentObjectModel(DOM),andCascading
StyleSheets(CSS),liveintheworldoftheWeb,wherenew
informationandtechnologieshitmillionsofpeoplein
milliseconds.Ifthetechniquerepresentsaninterestingidea
withpracticalmerit,agoodprobabilityexiststhatdevelopers

willatleastdiptheirtoesintothetechnology'swaters,ifnot
immediatelyaddthenewtooltotheircodearsenals.Second,
theAjaxfamilyoftechniquesarealreadywellknownandopen
source,orfreeofcharge;therefore,fewbarriersexisttotrying
themoutforatleastaprototypeversionofnewsoftware.
Third,anumberofuseful,well-knownapplicationsarebasedon
Ajax,suchasFlickrandGmail.Fourth,webusersarealready
accustomedtoanAjaxapplication'sdesktop-likeexperience,
wheretheapplicationcanmakeclient/serverconnections
withoutcompletelychangingthebrowserpage.
TherearenumerousotherreasonswhyAjaxisheretostay,
suchastheexcellentsupportforJavaScript,CSS,andDOM
providedbymodernbrowserssuchasFirefox,aswellasthe
prosandconsofusingMacromediaFlashforRichInternet
Applicationsinstead.


BuildingSingle-PageApplications
The"single-pageapplication"representedbyAjax,with
client/serverconnectionsthatdonotinterrupttheuser's
experienceanddynamicallychangeelementsindifferentweb
pageregions,isappropriatefornumeroususes,suchasblogs,
learningtools,onlinenewsletters,andsmallwebportalsor
communities.Manyofthesetypesofsitesarealreadybuilt
usingAjaxtechniques.Ajaxcanalsoimprovetheuser
experienceinlargeweb-basedclient/serverapplicationsthat
extendbeyondthesingle-pagemodel.
Thetimebetweentheconceptionofthisbookandthewritingof
thisprefacehasseenAjaxmorphintoasoftwareplatformthat
dominatesheadlinesontheWeb,nottomentionthebirthof

newacronymssuchasAjaj(AsynchronousJavaScriptand
JSON)andlingosuchas"Ajaxy"(asinanAjaxyserver
connection).Softwareinnovationsandhumanlanguageseemto
sharethesameorganicdynamic.




ExplainingAjax
AjaxHackswaswrittenbyyourstrulyandsevendifferent
contributors,manyofwhomareamongtheinnovators,
bloggers,andearlyadopterswhohelpedgiveAjaxanditsopen
sourcetoolstheboostitenjoystoday.Theyareseniorweb
engineersanddeveloperswhosehomesstretchfromBangalore
toSanFrancisco,ascopereflectingthediverseand
serendipitousnaturebywhichthewritersfoundthisbookand
thebookdiscovereditswriters.(SeetheCreditsformore
detailsonthesewriters.)
AjaxHackscollectsnotonlydozensofeasy-to-grasp,cuttingedgeexplorationsofAjaxtechnology,suchasGoogle/Yahoo!
mappingmash-ups,drag-and-dropbookstores,andsingle-page
webservicesapps,butalargenumberofhacksthatrepresent
practicaladviceforAjaxdevelopers.AjaxHacksalsointroduces
JavaScriptnewbiesandaficionadosaliketousefulcode
libraries,includingPrototype,Rico,andscript.aculo.us.Chapter
7focusesonapracticalandnewwebapplicationframework
withexcellentAjaxtoolsincludingRubyonRails.
Anumberofthecontributionsarehacksintheoriginal,clever
senseoftheterm,exploringtopicssuchasusingalgorithms
andFlashobjectstosimulateabrowserhistorylistandstore
Ajax-relateddataoffline,configuringApachetofixthe

XMLHttpRequestcross-domainrestrictions,runningasearchengine
insideyourbrowser,andmashingupYahoo!Mapswitha
location-to-URLservicecalledGeoURL.
Someofthecontributedhacksillustratecoolwebcontrolsand
embeddedscripts,suchasahackthatscriptsanauto-complete
fieldfromscratch,ahackthatcreatesJavaScriptbookmarklets
thatdonothavesizelimitations,andanotherthatcreatesan
RSSfeedreaderforanAjaxapplication.Thesearehacksthat
pushtheenvelope,justasweapproachthecuspofthisweb


model'sformulation.Atthesametime,webdeveloperscan
adaptanumberofthisbook'shacks,someofwhichare
distributedasopensourcelibraries,fortheirownapplications.




HowtoUseThisBook
Youcanreadthisbookfromcovertocoverifyoulike,butfor
themostpart,eachhackstandsonitsown,sofeelfreeto
browseandjumptothedifferentsectionsthatinterestyou
most.Ifthere'saprerequisiteyouneedtoknowabout,across
referencewillguideyoutotherighthack.So,feelfreeto
browse,flippingaroundtowhateversectionsinterestyoumost.


HowThisBookIsOrganized
Thebookisdividedintoseveralchapters,organizedbysubject:

Chapter1,AjaxBasics
WhatisAjax?Thischapterbeginswithasynopsisofthe
groupofwell-knowntechnologiesthatmakeupAjax.The
chapter'shacksintroducetheXMLHttpRequestJavaScriptobject
anditspropertiesandmethods,thendelveintothemeatof
thematter,suchassendingGETandPOSTrequests,aswell
asreceivingdatainplaintext,XML,andJSONformat.This
chapteralsoillustratesthedynamicscriptingofCSSstyles
inAjaxapplications.Lettheuserschangethecolorsand
fontsinsidethebrowserpage!

Chapter2,WebForms
WebformshavecertainlychangedintheAjaxworld.As
revealedinthischapter'shacks,itistypicalnowtosubmit
formdataandtobuildformwidgetssuchasselectlistsand
checkboxgroupsusingserverdatafetchedinthe
backgroundwithXMLHttpRequest.Becausethepagedoesn't
havetobecompletelyrebuiltfromaserverresponse,the
userexperiencesfewapplicationdelays.Thesehacksshow
howtosubmittextfromformfieldsandtextareasand
displayservervaluesinthosefields,withoutmakingthe
userclickasubmitbutton.Thehacksalsogeneratevarious
elements,suchasselectlistsandunorderedlists,using
XMLHttpRequestanddatathatisdynamicallyaccessedfroma
server.


Chapter3,Validation
Ajaxapplicationscancutdownonserverhitsbyvalidating
theformatofemailaddresses,creditcardnumbers,zip

codes,andothertypesofdatathatusersenterintoweb
formsbeforesendingthedata.Aservercomponentis
obviouslynecessaryforfinalcreditcardvalidationinarealworldapplication;however,theapplicationmayimplement
a"firstlayerofdefense,"asinthesehacks,byvalidating
theformatsoftext-fieldvalueswithJavaScriptregular
expressions.

Chapter4,PowerHacksforWebDevelopers
Webdevelopershaveneverhadcooler,easier-to-work-with
toolsthantheYahoo!andGooglewebAPIs.Thischapter
includesamash-upofGoogleMaps,Yahoo!Maps,and
Yahoo!drivingdirections,aswellasasoftwareinteraction
involvingYahoo!Mapsandalocation-to-URLservicecalled
GeoURL.Italsofeaturesmoreprosaic,pragmaticweb
hacks,suchassendinganemailwithXMLHttpRequest;viewing,
creating,andsendingHTTPcookieswithclient-sidescript;
fetchingapostalcodedynamicallywithoutalteringtheweb
page;aswellasdiscoveringanddisplayingthebrowser's
localeinformation.

Chapter5,DirectWebRemoting(DWR)forJavaJocks
DWRisaniftytoolkitthatallowsdeveloperstomake
remotecallstoJavaserverobjectsfromJavaScript,without
anyJavaappletsorplug-ins.DWRusesAjaxrequests
behindthescenes;thetoolkit'susers,however,donothave


todealwithXMLHttpRequestprogramming.Thesehacks
populateselectlistsfromJavaarraysandMaps;callcustom
JavaobjectsfromtheirJavaScriptproxiesorcounterparts;

anduseJavaScriptobjectstocallbuilt-inJavaobjects.This
chapterisatreatfordeveloperswhoareimmersedinboth
JavaandJavaScript.

Chapter6,HackAjaxwiththePrototypeandRicoLibraries
ThehacksinthischapterusePrototype,acoolopensource
JavaScriptlibrarythatincludesitsownAjaxtools.You'llsee
howtoupdateDOMelementsinawebpagewithserver
datausingPrototype'sAjax.Updaterobject,andhowtouse
thePeriodicalExecuterobjecttoexecuteAjaxrequestsat
timedintervalswhileanother"observer"objectmonitorsa
textfieldforchanges(imagine:auserentersdataintotext
fields,andaJavaScriptobjectautomaticallysendsthedata
offtopersistentserverstoragewheneverthefieldvalue
changes).Anotherhackinthischapterusestheopen
sourcelibraryRicoinaWeather.comwebservices
application.Finally,thechapter'slasthacksetsupadragand-dropbookstore,alsousingRico.

Chapter7,WorkwithAjaxandRubyonRails
LearnRubyonRails!RubyonRails(RoR)isanefficientand
well-designedwebapplicationframework,basedonthe
Model-View-Controllerdesignpattern,thatmadeitsdebut
in2005.Thischapterbeginswithasimplehackthathelps
yougetupandrunningwithRoR,thenmovesontoseveral
hacksthatillustrateRoR'sAjaxtools.Eachhackisaweb
applicationtaskwritteninRuby;forexample,oneofthe
hacksmonitorsaserverconnectionanddisplaysthestatus
intheclient.RoRbundlesPrototypewiththeframework,

thenwrapsthesetupoftheAjaxobjectsintoitsowneasyto-learn,embeddedscriptlanguage.Getreadytoreadalot
ofRubycode,atreatforthosewhomaybenewtothis
elegantandpowerfultool!

Chapter8,Savorthescript.aculo.usJavaScriptLibrary
script.aculo.usisanotheropensourceJavaScriptlibrary
builtonPrototype.Itoffersabroadmenuofusefuleffects
andcontrolsfordevelopers.ThesehackscreateaMacOS
Xstyleloginboxthat"shakes"inresponsetoinvalidlogins;
anauto-completefieldbasedonascript.aculo.usobject;a
controlthatallowstheusertoedittextualcontentinthe
browserandthensavethechangesonaserver,withouta
webpageroundtrip;and,justforfun,awebformthat
disappearsinapuffofsmokewhenit'ssubmitted.

Chapter9,OptionsandEfficiencies
Thesehacksprovideseveraltipsforreal-worldAjax
developers.Ironically,severalhacksillustratehowtoavoid
usingXMLHttpRequesttohittheserver:you'llseehowtoruna
searchengineinsidethebrowser,cachedatawith
JavaScript,and"fix"thebrowserbackbuttoninanAjax
applicationbyinternallystoringandaccessingstate.These
hacksalsorecommendwaystocombinecodelibrariesto
increasedownloadspeed,obfuscateorpartiallyobscure
JavaScriptcodetoprotectproprietaryscripting,setatimer
forabortinganAjaxrequest,aswellasdynamicallyrequest
datainJavaScriptObjectNotation(JSON)formatusingthe
HTMLscripttag.

ConventionsUsedinThisBook
Thefollowingisalistofthetypographicalconventionsusedin
thisbook:

Italics
UsedtoindicateURLs,filenames,filenameextensions,and
directory/foldernames,e.g.,apathinthefilesystem
appearsas/Developer/Applications

Constantwidth
Usedtoshowcodeexamples,thecontentsoffiles,console
output,aswellasthenamesofvariables,commands,and
othercodeexcerpts

Constantwidthbold
Usedtohighlightportionsofcode

Graytype
Usedtoindicateacrossreferencewithinthetext
Youshouldpayspecialattentiontonotessetapartfromthe
textwiththefollowingicons:


Thisisatip,suggestion,orgeneralnote.Itcontainsuseful
supplementaryinformationaboutthetopicathand.

Thisisawarningornoteofcaution,oftenindicatingthatsomething
mightbreakifyou'renotcareful,possiblyquitebadly.

Thethermometericons,foundnexttoeachhack,indicatethe

relativecomplexityofthehack:
Wheneverpossible,thehacksinthisbookarenotplatformspecific,whichmeansyoucanusethemonLinux,Macintosh,
andWindowsmachines.However,somethingsarepossibleonly
onaparticularplatform.