The abstract operation MakeConstructor takes argument _F_ (a function object) and optional arguments _writablePrototype_ (a Boolean) and _prototype_ (an Object). It converts _F_ into a constructor. It performs the following steps when called:
- 1. Assert: _F_ is an ECMAScript function object.
- 1. Assert: IsConstructor(_F_) is *false*.
- 1. Assert: _F_ is an extensible object that does not have a *"prototype"* own property.
- 1. Set _F_.[[Construct]] to the definition specified in .
+ 1. Assert: _F_ is an ECMAScript function object or a built-in function object.
+ 1. If _F_ is an ECMAScript function object, then
+ 1. Assert: IsConstructor(_F_) is *false*.
+ 1. Assert: _F_ is an extensible object that does not have a *"prototype"* own property.
+ 1. Set _F_.[[Construct]] to the definition specified in .
1. Set _F_.[[ConstructorKind]] to ~base~.
1. If _writablePrototype_ is not present, set _writablePrototype_ to *true*.
1. If _prototype_ is not present, then
@@ -11158,7 +11163,7 @@ CreateBuiltinFunction ( _steps_, _length_, _name_, _internalSlotsList_ [ , _
The abstract operation CreateBuiltinFunction takes arguments _steps_, _length_, _name_, and _internalSlotsList_ (a List of names of internal slots) and optional arguments _realm_, _prototype_, and _prefix_. _internalSlotsList_ contains the names of additional internal slots that must be defined as part of the object. This operation creates a built-in function object. It performs the following steps when called:
1. Assert: _steps_ is either a set of algorithm steps or other definition of a function's behaviour provided in this specification.
- 1. If _realm_ is not present, set _realm_ to the current Realm Record.
+ 1. If _realm_ is not present or _realm_ is ~empty~, set _realm_ to the current Realm Record.
1. Assert: _realm_ is a Realm Record.
1. If _prototype_ is not present, set _prototype_ to _realm_.[[Intrinsics]].[[%Function.prototype%]].
1. Let _func_ be a new built-in function object that when called performs the action described by _steps_. The new function object has internal slots whose names are the elements of _internalSlotsList_, and an [[InitialName]] internal slot.
@@ -20703,23 +20708,18 @@ Runtime Semantics: ClassDefinitionEvaluation
1. Let _proto_ be ! OrdinaryObjectCreate(_protoParent_).
1. If |ClassBody_opt| is not present, let _constructor_ be ~empty~.
1. Else, let _constructor_ be ConstructorMethod of |ClassBody|.
- 1. If _constructor_ is ~empty~, then
- 1. If |ClassHeritage_opt| is present, then
- 1. Let _constructorText_ be the source text
- constructor(...args) { super(...args); }
- 1. Else,
- 1. Let _constructorText_ be the source text
- constructor() {}
- 1. Set _constructor_ to ParseText(_constructorText_, |MethodDefinition[~Yield, ~Await]|).
- 1. Assert: _constructor_ is a Parse Node.
1. Set the running execution context's LexicalEnvironment to _classScope_.
- 1. Let _constructorInfo_ be ! DefineMethod of _constructor_ with arguments _proto_ and _constructorParent_.
- 1. Let _F_ be _constructorInfo_.[[Closure]].
- 1. Perform SetFunctionName(_F_, _className_).
- 1. Perform MakeConstructor(_F_, *false*, _proto_).
+ 1. If _constructor_ is ~empty~, then
+ 1. Let _steps_ be the algorithm steps defined in .
+ 1. Let _F_ be ! CreateBuiltinFunction(_steps_, 0, _className_, « [[ConstructorKind]], [[SourceText]] », ~empty~, _constructorParent_).
+ 1. Else,
+ 1. Let _constructorInfo_ be ! DefineMethod of _constructor_ with arguments _proto_ and _constructorParent_.
+ 1. Let _F_ be _constructorInfo_.[[Closure]].
+ 1. Perform ! MakeClassConstructor(_F_).
+ 1. Perform ! SetFunctionName(_F_, _className_).
+ 1. Perform ! MakeConstructor(_F_, *false*, _proto_).
1. If |ClassHeritage_opt| is present, set _F_.[[ConstructorKind]] to ~derived~.
- 1. Perform MakeClassConstructor(_F_).
- 1. Perform CreateMethodProperty(_proto_, *"constructor"*, _F_).
+ 1. Perform ! CreateMethodProperty(_proto_, *"constructor"*, _F_).
1. If |ClassBody_opt| is not present, let _methods_ be a new empty List.
1. Else, let _methods_ be NonConstructorMethodDefinitions of |ClassBody|.
1. For each |ClassElement| _m_ of _methods_, do
@@ -20735,6 +20735,24 @@ Runtime Semantics: ClassDefinitionEvaluation
1. Perform _classScope_.InitializeBinding(_classBinding_, _F_).
1. Return _F_.
+
+
+ Default Constructor Functions
+ When a Default Constructor Function is called with zero or more arguments which form the rest parameter ..._args_, the following steps are taken:
+
+ 1. If NewTarget is *undefined*, throw a *TypeError* exception.
+ 1. Let _F_ be the active function object.
+ 1. If _F_.[[ConstructorKind]] is ~derived~, then
+ 1. NOTE: This branch behaves similarly to `constructor(...args) { super(...args); }`. The most notable distinction is that while the aforementioned ECMAScript source text observably calls the @@iterator method on `%Array.prototype%`, a Default Constructor Function does not.
+ 1. Let _func_ be ! _F_.[[GetPrototypeOf]]().
+ 1. If IsConstructor(_func_) is *false*, throw a *TypeError* exception.
+ 1. Return ? Construct(_func_, _args_, NewTarget).
+ 1. Else,
+ 1. NOTE: This branch behaves similarly to `constructor() {}`.
+ 1. Return ? OrdinaryCreateFromConstructor(NewTarget, *"%Object.prototype%"*).
+
+ The *"length"* property of a default constructor function is *+0*𝔽.
+
@@ -25192,9 +25210,9 @@ Function.prototype.toString ( )
When the `toString` method is called, the following steps are taken:
1. Let _func_ be the *this* value.
- 1. If _func_ is a built-in function object, return an implementation-defined String source code representation of _func_. The representation must have the syntax of a |NativeFunction|. Additionally, if _func_ has an [[InitialName]] internal slot and _func_.[[InitialName]] is a String, the portion of the returned String that would be matched by |NativeFunctionAccessor?| |PropertyName| must be the value of _func_.[[InitialName]].
1. If Type(_func_) is Object and _func_ has a [[SourceText]] internal slot and _func_.[[SourceText]] is a sequence of Unicode code points and ! HostHasSourceTextAvailable(_func_) is *true*, then
1. Return ! CodePointsToString(_func_.[[SourceText]]).
+ 1. If _func_ is a built-in function object, return an implementation-defined String source code representation of _func_. The representation must have the syntax of a |NativeFunction|. Additionally, if _func_ has an [[InitialName]] internal slot and _func_.[[InitialName]] is a String, the portion of the returned String that would be matched by |NativeFunctionAccessor?| |PropertyName| must be the value of _func_.[[InitialName]].
1. If Type(_func_) is Object and IsCallable(_func_) is *true*, return an implementation-defined String source code representation of _func_. The representation must have the syntax of a |NativeFunction|.
1. Throw a *TypeError* exception.