Reference number ECMA-123:2009

Ecma International 2009

ECMA-262 8th Edition / June 2017

ECMAScript 2017 Language Specification

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ii Ecma International 2017

Introduction1Scope2Conformance3NormativeReferences4Overview4.1WebScripting4.2ECMAScriptOverview4.2.1Objects4.2.2TheStrictVariantofECMAScript

4.3TermsandDeinitions4.3.1type4.3.2primitivevalue4.3.3object4.3.4constructor4.3.5prototype4.3.6ordinaryobject4.3.7exoticobject4.3.8standardobject4.3.9builtinobject4.3.10undeinedvalue4.3.11Undeinedtype4.3.12nullvalue4.3.13Nulltype4.3.14Booleanvalue4.3.15Booleantype4.3.16Booleanobject4.3.17Stringvalue4.3.18Stringtype4.3.19Stringobject4.3.20Numbervalue4.3.21Numbertype4.3.22Numberobject4.3.23Ininity

ECMAScript2017LanguageSpeciicationTableofContents

4.3.24NaN4.3.25Symbolvalue4.3.26Symboltype4.3.27Symbolobject4.3.28function4.3.29builtinfunction4.3.30property4.3.31method4.3.32builtinmethod4.3.33attribute4.3.34ownproperty4.3.35inheritedproperty

4.4OrganizationofThisSpeciication5NotationalConventions5.1SyntacticandLexicalGrammars5.1.1ContextFreeGrammars5.1.2TheLexicalandRegExpGrammars5.1.3TheNumericStringGrammar5.1.4TheSyntacticGrammar5.1.5GrammarNotation

5.2AlgorithmConventions5.3StaticSemanticRules

6ECMAScriptDataTypesandValues6.1ECMAScriptLanguageTypes6.1.1TheUndeinedType6.1.2TheNullType6.1.3TheBooleanType6.1.4TheStringType6.1.5TheSymbolType6.1.5.1WellKnownSymbols

6.1.6TheNumberType6.1.7TheObjectType6.1.7.1PropertyAttributes6.1.7.2ObjectInternalMethodsandInternalSlots6.1.7.3InvariantsoftheEssentialInternalMethods6.1.7.4WellKnownIntrinsicObjects

6.2ECMAScriptSpeciicationTypes6.2.1TheListandRecordSpeciicationTypes6.2.2TheSetandRelationSpeciicationTypes6.2.3TheCompletionRecordSpeciicationType

6.2.3.1NormalCompletion6.2.3.2ImplicitCompletionValues6.2.3.3ThrowanException6.2.3.4ReturnIfAbrupt6.2.3.5UpdateEmpty(completionRecord,value)

6.2.4TheReferenceSpeciicationType6.2.4.1GetValue(V)6.2.4.2PutValue(V,W)6.2.4.3GetThisValue(V)6.2.4.4InitializeReferencedBinding(V,W)

6.2.5ThePropertyDescriptorSpeciicationType6.2.5.1IsAccessorDescriptor(Desc)6.2.5.2IsDataDescriptor(Desc)6.2.5.3IsGenericDescriptor(Desc)6.2.5.4FromPropertyDescriptor(Desc)6.2.5.5ToPropertyDescriptor(Obj)6.2.5.6CompletePropertyDescriptor(Desc)

6.2.6TheLexicalEnvironmentandEnvironmentRecordSpeciicationTypes6.2.7DataBlocks6.2.7.1CreateByteDataBlock(size)6.2.7.2CreateSharedByteDataBlock(size)6.2.7.3CopyDataBlockBytes(toBlock,toIndex,fromBlock,fromIndex,count)

7AbstractOperations7.1TypeConversion7.1.1ToPrimitive(input[,PreferredType])7.1.1.1OrdinaryToPrimitive(O,hint)

7.1.2ToBoolean(argument)7.1.3ToNumber(argument)7.1.3.1ToNumberAppliedtotheStringType7.1.3.1.1RS:MV

7.1.4ToInteger(argument)7.1.5ToInt32(argument)7.1.6ToUint32(argument)7.1.7ToInt16(argument)7.1.8ToUint16(argument)7.1.9ToInt8(argument)7.1.10ToUint8(argument)7.1.11ToUint8Clamp(argument)7.1.12ToString(argument)7.1.12.1ToStringAppliedtotheNumberType

7.1.13ToObject(argument)7.1.14ToPropertyKey(argument)7.1.15ToLength(argument)7.1.16CanonicalNumericIndexString(argument)7.1.17ToIndex(value)

7.2TestingandComparisonOperations7.2.1RequireObjectCoercible(argument)7.2.2IsArray(argument)7.2.3IsCallable(argument)7.2.4IsConstructor(argument)7.2.5IsExtensible(O)7.2.6IsInteger(argument)7.2.7IsPropertyKey(argument)7.2.8IsRegExp(argument)7.2.9SameValue(x,y)7.2.10SameValueZero(x,y)7.2.11SameValueNonNumber(x,y)7.2.12AbstractRelationalComparison7.2.13AbstractEqualityComparison7.2.14StrictEqualityComparison

7.3OperationsonObjects7.3.1Get(O,P)7.3.2GetV(V,P)7.3.3Set(O,P,V,Throw)7.3.4CreateDataProperty(O,P,V)7.3.5CreateMethodProperty(O,P,V)7.3.6CreateDataPropertyOrThrow(O,P,V)7.3.7DeinePropertyOrThrow(O,P,desc)7.3.8DeletePropertyOrThrow(O,P)7.3.9GetMethod(V,P)7.3.10HasProperty(O,P)7.3.11HasOwnProperty(O,P)7.3.12Call(F,V[,argumentsList])7.3.13Construct(F[,argumentsList[,newTarget]])7.3.14SetIntegrityLevel(O,level)7.3.15TestIntegrityLevel(O,level)7.3.16CreateArrayFromList(elements)7.3.17CreateListFromArrayLike(obj[,elementTypes])7.3.18Invoke(V,P[,argumentsList])7.3.19OrdinaryHasInstance(C,O)

7.3.20SpeciesConstructor(O,defaultConstructor)7.3.21EnumerableOwnProperties(O,kind)7.3.22GetFunctionRealm(obj)

7.4OperationsonIteratorObjects7.4.1GetIterator(obj[,method])7.4.2IteratorNext(iterator[,value])7.4.3IteratorComplete(iterResult)7.4.4IteratorValue(iterResult)7.4.5IteratorStep(iterator)7.4.6IteratorClose(iterator,completion)7.4.7CreateIterResultObject(value,done)7.4.8CreateListIterator(list)7.4.8.1ListIteratornext()

8ExecutableCodeandExecutionContexts8.1LexicalEnvironments8.1.1EnvironmentRecords8.1.1.1DeclarativeEnvironmentRecords8.1.1.1.1HasBinding(N)8.1.1.1.2CreateMutableBinding(N,D)8.1.1.1.3CreateImmutableBinding(N,S)8.1.1.1.4InitializeBinding(N,V)8.1.1.1.5SetMutableBinding(N,V,S)8.1.1.1.6GetBindingValue(N,S)8.1.1.1.7DeleteBinding(N)8.1.1.1.8HasThisBinding()8.1.1.1.9HasSuperBinding()8.1.1.1.10WithBaseObject()

8.1.1.2ObjectEnvironmentRecords8.1.1.2.1HasBinding(N)8.1.1.2.2CreateMutableBinding(N,D)8.1.1.2.3CreateImmutableBinding(N,S)8.1.1.2.4InitializeBinding(N,V)8.1.1.2.5SetMutableBinding(N,V,S)8.1.1.2.6GetBindingValue(N,S)8.1.1.2.7DeleteBindin