The creator of the Object.prototype

Question

The creator of the Object.prototype

Within the realm of JavaScript, each object acquires its properties and methods through a unique prototype, with these prototypes themselves taking the form of objects.

This results in an inheritance system known as the prototype chain, where (Object.prototype) serves as the topmost element (followed by null, which lacks any properties or methods), and all other objects inherit from it, unless changes are made to the prototype chain.

If (Object.prototype) is indeed an object, what exactly serves as its constructor?

In other words, what should be placed within this expression in order for it to return true:

Object.prototype instanceof .....

javascript oop prototypal-inheritance

Answer 1

Answer №1

Extracted from the "this and Object Prototypes" book in the "You don't know JS" series by Kyle Simpsion

function Foo() {
    // ...
}

Foo.prototype.constructor === Foo; // true

var a = new Foo();
a.constructor === Foo; // true

At the time of declaration on line 1, the `Foo.prototype` object automatically receives a public, non-enumerable property called `.constructor`, which is a reference back to the function (Foo). When we create object `a` with the `new Foo()` constructor call, we notice that it also has a `.constructor` property pointing back to the creating function.

Note: Contrary to appearance, `a` does not have a `.constructor` property itself, even though `a.constructor` does point to `Foo`. The concept of "constructed by" is more nuanced than it seems at first glance.

...

"Objects in JavaScript are linked together through an internal [[Prototype]] property, which simply references another object."

Therefore, Object.prototype is actually not an object. Regarding the question about instanceof:

var a = new Function();
a.prototype instanceof Object; //true
var b = new String();
b.prototype instanceof Object; //false

Answer 2

Extracted from the "this and Object Prototypes" book in the "You don't know JS" series by Kyle Simpsion

function Foo() {
    // ...
}

Foo.prototype.constructor === Foo; // true

var a = new Foo();
a.constructor === Foo; // true

At the time of declaration on line 1, the `Foo.prototype` object automatically receives a public, non-enumerable property called `.constructor`, which is a reference back to the function (Foo). When we create object `a` with the `new Foo()` constructor call, we notice that it also has a `.constructor` property pointing back to the creating function.

Note: Contrary to appearance, `a` does not have a `.constructor` property itself, even though `a.constructor` does point to `Foo`. The concept of "constructed by" is more nuanced than it seems at first glance.

...

"Objects in JavaScript are linked together through an internal [[Prototype]] property, which simply references another object."

Therefore, Object.prototype is actually not an object. Regarding the question about instanceof:

var a = new Function();
a.prototype instanceof Object; //true
var b = new String();
b.prototype instanceof Object; //false

The creator of the Object.prototype

Answer №1

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