What is - function Empty() - in javascript ? [duplicate]

Question

I have this function :

function fff(){}

Which is a function which is an instance of Function constructor

so fff.__proto__ should show me : function Function() { [native code] }

But it doesn't.

It shows : function Empty() {}

It is only at the constructor property of __proto__ that I see function Function() { [native code] }

Question :

What is this function Empty() {} function
and why fff.__proto__ won't show me : function Function() { [native code] } ?

nb I know that __proto__ is the actual object that is used in the lookup chain to resolve methods, etc. prototype is the object that is used to build __proto__ when you create an object with new.

But again : function fff is a function which is instantiated behind the scenes by newing Function constructor....so ?

Answer 1

You're misunderstanding __proto__.

__proto__ returns the prototype value that the object inherits; not its constructor.

All functions (including Function itself) inherit Function.prototype.
Thus, Function.__proto__ === Function.prototype is true.
This object is specified in section 15.3.4 of the spec:

The Function prototype object is itself a Function object (its [[Class]] is "Function") that, when invoked, accepts any arguments and returns undefined.

See also

15.3.4.2 Function.prototype.toString ( )

An implementation-dependent representation of the function is returned. This representation has the syntax of a FunctionDeclaration. Note in particular that the use and placement of white space, line terminators, and semicolons within the representation String is implementation-dependent.

The toString function is not generic; it throws a TypeError exception if its this value is not a Function object. Therefore, it cannot be transferred to other kinds of objects for use as a method.