JavaScript的Function详细

Function(Built-inObject)
Function(內置對象)
FunctionistheobjectfromwhichJavaScriptfunctionsarederived.Functionsarefirst-classdatatypesinJavaScript,sotheymaybeassignedtovariablesandpassedtofunctionsasyouwouldanyotherpieceofdata.Functionsare,ofcourse,referencetypes.

TheFunctionobjectprovidesbothstaticpropertieslikelengthandpropertiesthatconveyusefulinformationduringtheexecutionofthefunction,forexample,thearguments[]array.

Constructor
varinstanceName=newFunction([arg1[,arg2[,...]],]body);

Thebodyparameterisastringcontainingthetextthatmakesupthebodyofthefunction.TheoptionalargNsarethenamesoftheformalparametersthefunctionaccepts.Forexample:

varmyAdd=newFunction(x,y,returnx+y);
varsum=myAdd(17,34);

Properties

arguments[]Animplicitlyfilledandimplicitlyavailable(directlyusableasargumentsfromwithinthefunction)arrayofparametersthatwerepassedtothefunction.Thisvalueisnullifthefunctionisnotcurrentlyexecuting.(IE4+(JScript2.0+),MOZ,N3+(JavaScript1.1+),ECMAEdition1)

arguments.calleeReferencetothecurrentfunction.Thispropertyisdeprecated.(N4+,MOZ,IE5.5+)

arguments.callerReferencetothefunctionthatinvokedthecurrentfunction.Thispropertyisdeprecated.(N3,IE4+)

arguments.lengthThenumberofargumentsthatwerepassedtothefunction.(IE4+(JScript2.0+),MOZ,N3+(JavaScript1.1+),ECMAEdition1)

arityNumericvalueindicatinghowmanyargumentsthefunctionexpects.Thispropertyisdeprecated.(N4+,MOZ)

callerReferencetothefunctionthatinvokedthecurrentfunctionornullifcalledfromtheglobalcontext.(IE4+(JScript2.0+),MOZ,N3+)

constructorReferencetotheconstructorobjectthatcreatedtheobject.(IE4+(JScript2.0+),N3+(JavaScript1.1+),ECMAEdition1)

lengthThenumberofargumentsthefunctionexpectstobepassed.(IE4+(JScript2.0+),N3+(JavaScript1.1+),ECMAEdition1)

prototypeReferencetotheobjectsprototype.(IE4+(JScript2.0+),N3+(JavaScript1.1+),ECMAEdition1)

Methods
apply(thisArg[,argArray])InvokesthefunctionwiththeobjectreferencedbythisArgasitscontext(soreferencestothisinthefunctionreferencethisArg).TheoptionalparameterargArraycontainsthelistofparameterstopasstothefunctionasitisinvoked.(IE5.5+(JScript5.5+),N4.06+(JavaScript1.3+),MOZ,ECMAEdition3)

call(thisArg[,arg1[,arg2[,...]]])InvokesthefunctionwiththeobjectreferencedbythisArgasitscontext(soreferencestothisinthefunctionreferencethisArg).TheoptionalparametersargNarepassedtothefunctionasitisinvoked.(IE5.5+(JScript5.5+),N4.06+(JavaScript1.3+),MOZ,ECMAEdition3)

toString()Returnsthestringversionofthefunctionsource.Thebodyofbuilt-inandbrowserobjectswilltypicallyberepresentedbythevalue[nativecode].(IE4+(JScript2.0+),N3+(JavaScript1.1+),MOZ,ECMAEdition1)

valueOf()Returnsthestringversionofthefunctionsource.Thebodyofbuilt-inandbrowserobjectswilltypicallyberepresentedbythevalue[nativecode].(IE4+(JScript2.0+),N3+(JavaScript1.1+),MOZ,ECMAEdition1)

Support
SupportedinIE4+(JScript2.0+),N3+(JavaScript1.1+),MOZ,ECMAScriptEdition1.

Notes
Generalexamplesoffunctionsarefoundthroughoutthebook,butseeChapter5forexamplesoftheadvancedaspectsoffunctionsandtheFunctionobject.