---
id: 587d7db0367417b2b2512b82
title: Understand the Prototype Chain
challengeType: 1
---
## Description
All objects in JavaScript (with a few exceptions) have a prototype. Also, an object’s prototype itself is an object.
function Bird(name) {
this.name = name;
}
typeof Bird.prototype; // => object
Because a prototype is an object, a prototype can have its own prototype! In this case, the prototype of Bird.prototype is Object.prototype:
Object.prototype.isPrototypeOf(Bird.prototype);
// returns true
How is this useful? You may recall the hasOwnProperty method from a previous challenge:
let duck = new Bird("Donald");
duck.hasOwnProperty("name"); // => true
The hasOwnProperty method is defined in Object.prototype, which can be accessed by Bird.prototype, which can then be accessed by duck. This is an example of the prototype chain.
In this prototype chain, Bird is the supertype for duck, while duck is the subtype. Object is a supertype for both Bird and duck.
Object is a supertype for all objects in JavaScript. Therefore, any object can use the hasOwnProperty method.
## Instructions
Modify the code to show the correct prototype chain.
## Tests
```yml
tests:
- text: Your code should show that Object.prototype is the prototype of Dog.prototype")
testString: assert(/Object\.prototype\.isPrototypeOf/.test(code), "Your code should show that Object.prototype is the prototype of Dog.prototype");
```
## Challenge Seed
```js
function Dog(name) {
this.name = name;
}
let beagle = new Dog("Snoopy");
Dog.prototype.isPrototypeOf(beagle); // => true
// Fix the code below so that it evaluates to true
???.isPrototypeOf(Dog.prototype);
```
## Solution
```js
function Dog(name) {
this.name = name;
}
let beagle = new Dog("Snoopy");
Dog.prototype.isPrototypeOf(beagle);
Object.prototype.isPrototypeOf(Dog.prototype);
```