---
id: 587d7db2367417b2b2512b89
title: Use a Mixin to Add Common Behavior Between Unrelated Objects
challengeType: 1
---
## Description
As you have seen, behavior is shared through inheritance. However, there are cases when inheritance is not the best solution. Inheritance does not work well for unrelated objects like Bird and Airplane. They can both fly, but a Bird is not a type of Airplane and vice versa.
For unrelated objects, it's better to use mixins. A mixin allows other objects to use a collection of functions.
let flyMixin = function(obj) {
obj.fly = function() {
console.log("Flying, wooosh!");
}
};
The flyMixin takes any object and gives it the fly method.
let bird = {
name: "Donald",
numLegs: 2
};
let plane = {
model: "777",
numPassengers: 524
};
flyMixin(bird);
flyMixin(plane);
Here bird and plane are passed into flyMixin, which then assigns the fly function to each object. Now bird and plane can both fly:
bird.fly(); // prints "Flying, wooosh!"
plane.fly(); // prints "Flying, wooosh!"
Note how the mixin allows for the same fly method to be reused by unrelated objects bird and plane.
## Instructions
Create a mixin named glideMixin that defines a method named glide. Then use the glideMixin to give both bird and boat the ability to glide.
## Tests
```yml
tests:
- text: Your code should declare a glideMixin variable that is a function.
testString: 'assert(typeof glideMixin === "function", "Your code should declare a glideMixin variable that is a function.");'
- text: Your code should use the glideMixin on the bird object to give it the glide method.
testString: 'assert(typeof bird.glide === "function", "Your code should use the glideMixin on the bird object to give it the glide method.");'
- text: Your code should use the glideMixin on the boat object to give it the glide method.
testString: 'assert(typeof boat.glide === "function", "Your code should use the glideMixin on the boat object to give it the glide method.");'
```
## Challenge Seed
```js
let bird = {
name: "Donald",
numLegs: 2
};
let boat = {
name: "Warrior",
type: "race-boat"
};
// Add your code below this line
```
## Solution
```js
let bird = {
name: "Donald",
numLegs: 2
};
let boat = {
name: "Warrior",
type: "race-boat"
};
function glideMixin (obj) {
obj.glide = () => 'Gliding!';
}
glideMixin(bird);
glideMixin(boat);
```