Core JavaScript Guide

comp.sysTCP/IPdirectoryserverWorldWideWebwwPersonalIStoreProxymerchantsystemHTML(Netscape)anditslicensorsretainallownershiprightstothesoftwareprogramsofferedbyNetscape(referredtohereinasSoftware)andrelateddocumentation.UseoftheSoftwareandrelateddocumentationisgovernedbythelicenseagreementaccompanyingtheSoftwareandapplicablecopyrightlaw.Yourrighttocopythisdocumentationislimitedbycopyrightlaw.Makingunauthorizedcopies,adaptations,orcompilationworksisprohibitedandconstitutesapunishableviolationofthelaw.Netscapemayrevisethisdocumentationfromtimetotimewithoutnotice.THISDOCUMENTATIONISPROVIDEDASISWITHOUTWARRANTYOFANYKIND.INNOEVENTSHALLNETSCAPEBELIABLEFORANYLOSSOFPROFITS,LOSSOFBUSINESS,LOSSOFUSEORDATA,INTERRUPTIONOFBUSINESS,ORFORINDIRECT,SPECIAL,INCIDENTAL,ORCONSEQUENTIALDAMAGESOFANYKIND,ARISINGFROMANYERRORINTHISDOCUMENTATION.TheSoftwareanddocumentationarecopyright©1994-1998NetscapeCommunicationsCorporation.Allrightsreserved.TheSoftwarecontainsJavaScriptsoftwaretechnologyinventedandimplementedbyNetscapeCommunicationsCorporation.TheJavaScriptnameisatrademarkorregisteredtrademarkofSunMicrosystems,Inc.intheUnitedStatesandothercountriesandisusedunderlicense.Netscape,NetscapeNavigator,NetscapeCertificateServer,NetscapeDevEdge,NetscapeFastTrackServer,NetscapeONE,SuiteSpotandtheNetscapeNandShip’sWheellogosareregisteredtrademarksofNetscapeCommunicationsCorporationintheUnitedStatesandothercountries.OtherNetscapelogos,productnames,andservicenamesarealsotrademarksofNetscapeCommunicationsCorporation,whichmayberegisteredinothercountries.Otherproductandbrandnamesaretrademarksoftheirrespectiveowners.Thedownloading,exportorreexportofNetscapesoftwareoranyunderlyinginformationortechnologymustbeinfullcompliancewithallUnitedStatesandotherapplicablelawsandregulations.AnyprovisionofNetscapesoftwareordocumentationtotheU.S.GovernmentiswithrestrictedrightsasdescribedinthelicenseagreementaccompanyingNetscapesoftware..Version1.4©1998NetscapeCommunicationsCorporation.AllRightsReservedPrintedintheUnitedStatesofAmerica.00999854321NetscapeCommunicationsCorporation,501EastMiddlefieldRoad,MountainView,CA94043RecycledandRecyclablePaper3NewFeaturesinthisReleaseJavaScriptversion1.4providesthefollowingnewfeaturesandenhancements:•Exceptionhandling.Youcanthrowandcatchexceptionsusingthethrowandtry...catchstatements.See“ExceptionHandlingStatements”onpage82.•Newoperatorsinandinstanceof.Theinoperatorreturnstrueifthespecifiedpropertyisinthespecifiedobject;see“in”onpage50.Theinstanceofoperatorreturnstrueifthespecifiedobjectisofthespecifiedobjecttype;see“instanceof”onpage50.•ChangestoLiveConnect.SeveralchangestoLiveConnectimprovethewayJavaandJavaScriptcodecommunicate:•JavaClassobjectsareautomaticallyconvertedtoinstancesofjava.lang.Classwhenyoupassthemasparameterstomethods.See“JavaClassobjects”onpage159.•Youcanpassaone-characterstringtoaJavamethodwhichrequiresanargumentoftypechar.See“ArgumentsofTypechar”onpage147.•IfyourJavaScriptcodeaccessesaJavadatamemberormethodandfails,theJavaexceptionispassedontoJavaScriptforyoutohandle.See“HandlingJavaExceptionsinJavaScript”onpage147.•EnhancementstotheJSExceptionclasschangethewayyouhandleJavaScriptexceptionsinyourJavacode.See“HandlingJavaScriptExceptionsinJava”onpage150.•ChangestotheFunctionobject.Youshouldnolongerspecifyafunctionnamewhenusingtheargumentsarray;theargumentsarrayisavariableandisnolongerapropertyofFunctionobjects.Thischangeimprovesperformance.See“UsingtheargumentsArray”onpage89.4CoreJavaScriptGuideContentsvContentsNewFeaturesinthisRelease.......................................................................3AboutthisBook..............................................................................................11NewFeaturesinthisRelease..............................................................................11WhatYouShouldAlreadyKnow.......................................................................11JavaScriptVersions..............................................................................................12WheretoFindJavaScriptInformation................................................................13DocumentConventions.......................................................................................14Chapter1JavaScriptOverview................................................................15WhatIsJavaScript?...............................................................................................16JavaScriptandJava..............................................................................................17DebuggingJavaScript..........................................................................................18VisualJavaScript.............................................................................................