Arguments 物件- JavaScript - MDN Web Docs - Mozilla

The arguments object is a local variable available within all (non-arrow) functions. You can refer to a function's arguments within the ... SkiptomaincontentSkiptosearchSkiptoselectlanguage給開發者的網頁技術文件JavaScriptJavaScript參考文件FunctionsArguments物件ArticleActions正體中文(繁體)ThispagewastranslatedfromEnglishbythecommunity.LearnmoreandjointheMDNWebDocscommunity.語法描述屬性範例規範瀏覽器相容性參見RelatedTopics JavaScript Tutorials: Completebeginners JavaScriptbasics JavaScriptfirststeps JavaScriptbuildingblocks IntroducingJavaScriptobjects JavaScriptGuide Introduction Grammarandtypes Controlflowanderrorhandling Loopsanditeration Functions Expressionsandoperators Numbersanddates Textformatting Regularexpressions Indexedcollections Keyedcollections Workingwithobjects Usingclasses Usingpromises Iteratorsandgenerators Metaprogramming JavaScriptmodules Intermediate Client-sideJavaScriptframeworks Client-sidewebAPIs Are-introductiontoJavaScript JavaScriptdatastructures Equalitycomparisonsandsameness Closures Advanced Inheritanceandtheprototypechain Strictmode JavaScripttypedarrays MemoryManagement ConcurrencymodelandEventLoop References: Built-inobjects 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Misc JavaScripttechnologiesoverview Lexicalgrammar JavaScriptdatastructures Enumerabilityandownershipofproperties Iterationprotocols Strictmode Transitioningtostrictmode Templateliterals Deprecatedfeatures 語法描述屬性範例規範瀏覽器相容性參見Arguments物件arguments物件是一個對應傳入函式之引數的類陣列（Array-like）物件。

語法arguments 描述 備註：如果你有在使用ES6語法，建議參考其餘參數。

備註：「類陣列(Array-like)」的意思是arguments一樣擁有length這項屬性，以及從0開始的索引，但是它沒有陣列內建的方法像是forEach()，或是map()。

Theargumentsobjectisalocalvariableavailablewithinall(non-arrow)functions.Youcanrefertoafunction'sargumentswithinthefunctionbyusingtheargumentsobject.Thisobjectcontainsanentryforeachargumentpassedtothefunction,thefirstentry'sindexstartingat0. Forexample,ifafunctionispassedthreearguments,youcanrefertothemasfollows: arguments[0] arguments[1] arguments[2] arguments也可以被指定： arguments[1]='newvalue'; arguments物件不是陣列。

它與陣列非常相似，但是它沒有除了length這個屬性以外的其他陣列屬性。

舉例，它沒有pop這個陣列方法。

然而，它依然可以被轉換為真正的陣列(Array)。

varargs=Array.prototype.slice.call(arguments); varargs=[].slice.call(arguments); //ES2015 constargs=Array.from(arguments); 警告：UsingsliceonargumentspreventsoptimizationsinsomeJavaScriptengines(V8forexample-moreinformation).Ifyoucareforthem,tryconstructinganewarraybyiteratingthroughtheargumentsobjectinstead.AnalternativewouldbetousethedespisedArrayconstructorasafunction: varargs=(arguments.length===1?[arguments[0]]:Array.apply(null,arguments)); Youcanusetheargumentsobjectifyoucallafunctionwithmoreargumentsthanitisformallydeclaredtoaccept.Thistechniqueisusefulforfunctionsthatcanbepassedavariablenumberofarguments.Usearguments.lengthtodeterminethenumberofargumentspassedtothefunction,andthenprocesseachargumentbyusingtheargumentsobject.Todeterminethenumberofparametersinthefunctionsignature,usetheFunction.lengthproperty.UsingtypeofwithArgumentsThetypeofargumentsreturns'object'. console.log(typeofarguments);//'object' Thetypeofindividualargumentscanbedeterminedwiththeuseofindexing. console.log(typeofarguments[0]);//thiswillreturnthetypeofindividualarguments. UsingtheSpreadSyntaxwithArgumentsYoucanalsousetheArray.from()methodorthespreadoperatortoconvertargumentstoarealArray: varargs=Array.from(arguments); varargs=[...arguments]; 屬性 arguments.callee Referencetothecurrentlyexecutingfunction. arguments.caller Deprecated Referencetothefunctionthatinvokedthecurrentlyexecutingfunction. arguments.length Referencetothenumberofargumentspassedtothefunction. arguments[@@iterator] ReturnsanewArrayIteratorobjectthatcontainsthevaluesforeachindexinthearguments. 範例DefiningafunctionthatconcatenatesseveralstringsThisexampledefinesafunctionthatconcatenatesseveralstrings.Theonlyformalargumentforthefunctionisastringthatspecifiesthecharactersthatseparatetheitemstoconcatenate.Thefunctionisdefinedasfollows: functionmyConcat(separator){ varargs=Array.prototype.slice.call(arguments,1); returnargs.join(separator); } Youcanpassanynumberofargumentstothisfunction,anditcreatesalistusingeachargumentasaniteminthelist. //returns"red,orange,blue" myConcat(',','red','orange','blue'); //returns"elephant;giraffe;lion;cheetah" myConcat(';','elephant','giraffe','lion','cheetah'); //returns"sage.basil.oregano.pepper.parsley" myConcat('.','sage','basil','oregano','pepper','parsley'); DefiningafunctionthatcreatesHTMLlistsThisexampledefinesafunctionthatcreatesastringcontainingHTMLforalist.Theonlyformalargumentforthefunctionisastringthatis"u"ifthelististobeunordered(bulleted),or"o"ifthelististobeordered(numbered).Thefunctionisdefinedasfollows: functionlist(type){ varresult='

'; varargs=Array.prototype.slice.call(arguments,1); result+=args.join('

'); result+='

'+type+'l>';//endlist returnresult; } Youcanpassanynumberofargumentstothisfunction,anditaddseachargumentasanitemtoalistofthetypeindicated.Forexample: varlistHTML=list('u','One','Two','Three'); /*listHTMLis: "

• One
• Two
• Three

" */ Rest,default,anddestructuredparametersTheargumentsobjectcanbeusedinconjunctionwithrest,default,anddestructuredparameters. functionfoo(...args){ returnargs; } foo(1,2,3);//[1,2,3] Whilethepresenceofrest,default,ordestructuredparametersdoesnotalterthebehavioroftheargumentsobjectinstrictmodecode,thereisasubtledifferencefornon-strictcode. Whenanon-strictfunctiondoesnotcontainrest,default,ordestructuredparameters,thenthevaluesintheargumentsobjectdotrackthevaluesofthearguments(andviceversa).Seethecodebelow: functionfunc(a){ arguments[0]=99;//updatingarguments[0]alsoupdatesa console.log(a); } func(10);//99 and functionfunc(a){ a=99;//updatingaalsoupdatesarguments[0] console.log(arguments[0]); } func(10);//99 Whenanon-strictfunctiondoescontainrest,default,ordestructuredparameters,thenthevaluesintheargumentsobjectdonottrackthevaluesofthearguments(andviceversa).Instead,theyreflecttheargumentsprovidedatthetimeofinvocation: functionfunc(a=55){ arguments[0]=99;//updatingarguments[0]doesnotalsoupdatea console.log(a); } func(10);//10 and functionfunc(a=55){ a=99;//updatingadoesnotalsoupdatearguments[0] console.log(arguments[0]); } func(10);//10 and functionfunc(a=55){ console.log(arguments[0]); } func();//undefined 規範SpecificationECMAScriptLanguageSpecification#sec-arguments-exotic-objects瀏覽器相容性BCDtablesonlyloadinthebrowser參見 Function Foundaproblemwiththispage?EditonGitHubSourceonGitHubReportaproblemwiththiscontentonGitHubWanttofixtheproblemyourself?SeeourContributionguide.Lastmodified:2022年8月20日,byMDNcontributors