I Don't Understand Object Oriented Programming - Understand the Prototype Chain

[Habushu]

Tell us what’s happening:
Hello everyone,

I pass this section because I read the instruction. but I don’t quite understand why

Dog.prototype.isPrototypeOf(beagle);

return true

and this one:

beagle.isPrototypeOf(Dog.prototype);

return false

Could someone explain it in a simple way please

Your code so far

function Dog(name) {
  this.name = name;
}

let beagle = new Dog("Snoopy");

Dog.prototype.isPrototypeOf(beagle);  // yields true

// Fix the code below so that it evaluates to true
beagle.isPrototypeOf(Dog.prototype);

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/105.0.0.0 Safari/537.36

Challenge: Object Oriented Programming - Understand the Prototype Chain

Link to the challenge:

freeCodeCamp.org

[admit8490]

What if I say:

every beagle is a dog? that is kinda true, right? At least in the context of this challenge, not going into english language details here.

So if I rephrase it in more ‘javascript’ fashion’, I can say that dog is a prototype of beagle.

And if I translate the question ‘is a dog a prototype of beagle?’ into javascript, I should write exactly this:

Dog.prototype.isPrototypeOf(beagle);

we defined beagle in the upper code as an instance of Dog. So, the above expression evaluates to true.

here is your code a bit modified, with some examples:

function Dog(name) {
  this.name = name;
}

function Car(name) {
  this.name = name;
}

let beagle = new Dog("Snoopy");
let ford = new Car("good old ford")

console.log(Dog.prototype.isPrototypeOf(beagle));//true

console.log(Car.prototype.isPrototypeOf(beagle))//false

console.log(Dog.prototype.isPrototypeOf(ford))//false

console.log(Car.prototype.isPrototypeOf(ford))//true

[Habushu]

I understand the example you gave, since it’s obvious difference.

I was confused with why Dog prototype isPrototypeOf beagle but not the otherway around. but I think I got it now. because Dog is supertype of beagle but not the vice versa. correct me if im wrong