javascript prototypes and inheritance

Question

My question is Object is last on prototype chain all objects inherit properties and methods from it how it is inherit methods from Function.prototype, why Object.__proto__ === Function.prototype // true, why Object.__proto__ is not null.

No normal object inherits from `Object` in javascript. They all inherit from `Object.prototype` (which is also the `Object.getPrototypeOf(Function.prototype)`). You will find that `Obect.getPrototypeOf(Object.prototype) === null` as expected. — Bergi, Sep 09 '20 at 20:40

score 0 · Answer 1 · answered Sep 09 '20 at 20:27

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The fundamental Object in JavaScript has to have a way for it to be instantiated, so it requires a prototype object to aid in lines like this:

let myObj = new Object();

And that is why Object.__proto__ is not null.

The Function object is a special type of object that facilitates object instantiation via a constructor and when used this way is known as a "constructor function". So, it makes sense for Object to inherit from a Function object so that object instances can be made.

answered Sep 09 '20 at 20:27

Scott Marcus

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its mean that Function and Object inherit methods and properties from each other ? – javascript lover Sep 09 '20 at 20:35
why Function is not last on prototype chain ? – javascript lover Sep 09 '20 at 20:37
@javascriptlover `Function` is the last of the prototype chain. As you correctly point out `Object._proto__ === Function()` – Scott Marcus Sep 09 '20 at 20:46
mdn says Object is last on prototype chain. – javascript lover Sep 09 '20 at 20:49
I think you are confusing `__proto__` and `prototype`. `__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 – Scott Marcus Sep 09 '20 at 20:52
@ScottMarcus What do you mean by "*The Function object is a special type of object that facilitates object instantiation via a constructor*"? – Bergi Sep 09 '20 at 21:05
I don't know if this helps or not, but `Object.getPrototypeOf(Object.getPrototypeOf(Object))` is `null`. `Object.getPrototypeOf(Object)` is a function, but not `Function`. – evolutionxbox Sep 09 '20 at 21:26
Why Function.__proto__.__proto__ === Object.prototype // true – javascript lover Sep 09 '20 at 21:30

score 0 · Answer 2 · answered Sep 09 '20 at 20:28

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Function is also an object. So it inherits from Object too.

But don't be confused by Object.__proto__. That's something the browser adds and isn't actually part of the language. So don't rely on it or use it.

Essentially, Function.prototype is Object.__proto__.

answered Sep 09 '20 at 20:28

Geuis

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why Function is not last on prototype chain ? – javascript lover Sep 09 '20 at 20:40
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Because Function inherits from Object. – Geuis Sep 09 '20 at 20:44
No, `Object` inherits from `Function`, which is implemented as native code. This is how/why objects have the ability to be called with the `new` keyword as constructor functions. Open your browser console and type: `Function.prototype;` and see what you get. – Scott Marcus Sep 09 '20 at 20:47
@ScottMarcus What Geuis meant is that Function is a subclass of Object, and all functions are objects. No, `Object` does not inherit from `Function`. At best, it does inherit from `Function.prototype`, and it's an `instanceof Function`. – Bergi Sep 09 '20 at 21:03
@ScottMarcus riiight. Bit rusty, I've been off work for a few months. Sorry. Yeah, Object does inherit from Function, which is why you can do `new Function()` and `new Object()`. But @Bergi is clarifying what I was trying to say originally. – Geuis Sep 09 '20 at 21:04

javascript prototypes and inheritance

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