---
id: 587d7daf367417b2b2512b7e
title: Understand the Constructor Property
challengeType: 1
---
## Description
There is a special constructor property located on the object instances duck and beagle that were created in the previous challenges:
let duck = new Bird();
let beagle = new Dog();
console.log(duck.constructor === Bird); //prints true
console.log(beagle.constructor === Dog); //prints true
Note that the constructor property is a reference to the constructor function that created the instance.
The advantage of the constructor property is that it's possible to check for this property to find out what kind of object it is. Here's an example of how this could be used:
function joinBirdFraternity(candidate) {
if (candidate.constructor === Bird) {
return true;
} else {
return false;
}
}
Note
Since the constructor property can be overwritten (which will be covered in the next two challenges) it’s generally better to use the instanceof method to check the type of an object.
## Instructions
Write a joinDogFraternity function that takes a candidate parameter and, using the constructor property, return true if the candidate is a Dog, otherwise return false.
## Tests
```yml
tests:
- text: joinDogFraternity should be defined as a function.
testString: 'assert(typeof(joinDogFraternity) === "function", "joinDogFraternity should be defined as a function.");'
- text: joinDogFraternity should return true ifcandidate is an instance of Dog.
testString: 'assert(joinDogFraternity(new Dog("")) === true, "joinDogFraternity should return true ifcandidate is an instance of Dog.");'
- text: joinDogFraternity should use the constructor property.
testString: 'assert(/\.constructor/.test(code) && !/instanceof/.test(code), "joinDogFraternity should use the constructor property.");'
```
## Challenge Seed
```js
function Dog(name) {
this.name = name;
}
// Add your code below this line
function joinDogFraternity(candidate) {
}
```
## Solution
```js
function Dog(name) {
this.name = name;
}
function joinDogFraternity(candidate) {
return candidate.constructor === Dog;
}
```