Function.prototype is a function

Question

I\'m digging into the Javascript prototype chain.
In order to document my findings, I\'ve drawn the following scheme:

Although most of the concepts are

Answer 1

In answer to your questions:

1) Function.prototype is a type of function because, according to ECMAScript 2015:

The Function prototype object is the intrinsic object %FunctionPrototype%. The Function prototype object is itself a built-in function object.

The Function prototype object is specified to be a function object to ensure compatibility with ECMAScript code that was created prior to the ECMAScript 2015 specification.

So the Function prototype object is only defined as a Function object to ensure compatability with older ECMAScript standards. The function doesn't actually do anything:

When invoked, it accepts any arguments and returns undefined.

http://www.ecma-international.org/ecma-262/6.0/#sec-properties-of-the-function-prototype-object

2) Regarding the prototype property:

The Function prototype object does not have a prototype property.

Same Source

This is unique since all functions usually possess a prototype property, however since the Function prototype object is only specified as a Function object to maintain compatability, it's behaviour is unlike that of regular functions.

I've created a JSFiddle with various tests in case it helps anyone:

http://jsfiddle.net/Ld0b39xz/

// We'll use 'Object.getPrototypeOf' to access [[prototype]]

// As you know, [[prototype]] of Object.prototype returns 'null'. 
console.log(Object.getPrototypeOf(Object.prototype));
// null

////////////////////////////////////////////////////////

// Let's take a closer look at Function.prototype
console.log(Function.prototype);
// Output:
// function(){}

// This is what the specs say should happen:
// "The Function prototype object is itself a built-in function object."

/////////////////////////////////////////////////////

// Let's see if this function has a 'prototype' property.
// All functions normally have a prototype property that initially
// references an empty object...except this one.
var fn = Function.prototype;
console.log(fn.prototype);
// Output:
// undefined

// This is expected, according to the specs:
// "The Function prototype object does not have a prototype property."

// It does have some properties such as 'name' and 'length',
// but not 'prototype'.

////////////////////////////////////////////////////////

// Let's see what [[prototype]] of Function.prototype returns.
console.log(Object.getPrototypeOf(Function.prototype));
// Output:
// Object{}

// Again this is expected:
// "The value of the [[Prototype]] internal slot of the
// Function prototype object is the intrinsic object %ObjectPrototype%"

/////////////////////////////////////////////////////////

// Now lets see what the [[Prototype]] of this object is:
console.log(Object.getPrototypeOf(Object.getPrototypeOf(Function.prototype)));
// Output:
// null

// We've come full circle since all the statement above is
// doing is looking for the prototoype of the native Object,
// which we already know is 'null' from our first test.