where is __proto__ for Number, Date, Boolean, Array

Question

I draw a picture based on prototype chain relationship.

but wonder where the __proto__ of Number, Date, Boolean, Array point to.

Your comment welcome

Answer 1

When in doubt, you can check the spec:

15.7.3 Properties of the Number Constructor

The value of the [[Prototype]] internal property of the Number constructor is the Function prototype object (15.3.4).

15.9.4 Properties of the Date Constructor

The value of the [[Prototype]] internal property of the Date constructor is the Function prototype object (15.3.4).

15.6.3 Properties of the Boolean Constructor

The value of the [[Prototype]] internal property of the Boolean constructor is the Function prototype object (15.3.4).

15.4.3 Properties of the Array Constructor

The value of the [[Prototype]] internal property of the Array constructor is the Function prototype object (15.3.4).

And the reasoning is that those objects are functions/constructors. So you may want to use function methods on them.

For example, a (bad) way to convert array-like objects to arrays:

Array.apply(void 0, {0: 'a', 1: 'b', 2: 'c', length: 3}) // ["a", "b", "c"]

Answer 2

Since all of those are functions (typeof Date = typeof Number = "function") it points to Function.prototype.

It's easy to verify by simply checking:

Date.__proto__ === Function.prototype; // true

This is the case because they are functions (you call them as functions), they contain all the things functions need to do (such as .call .bind and .apply)