freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/object-oriented-programming/use-a-mixin-to-add-common-behavior-between-unrelated-objects.md

---
id: 587d7db2367417b2b2512b89
title: Use a Mixin to Add Common Behavior Between Unrelated Objects
challengeType: 1
forumTopicId: 301331
dashedName: use-a-mixin-to-add-common-behavior-between-unrelated-objects
---

# --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 <dfn>mixins</dfn>. A mixin allows other objects to use a collection of functions.

```js
let flyMixin = function(obj) {
  obj.fly = function() {
    console.log("Flying, wooosh!");
  }
};
```

The `flyMixin` takes any object and gives it the `fly` method.

```js
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:

```js
bird.fly();
plane.fly();
```

The console would display the string `Flying, wooosh!` twice, once for each `.fly()` call.

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.

# --hints--

Your code should declare a `glideMixin` variable that is a function.

```js
assert(typeof glideMixin === 'function');
```

Your code should use the `glideMixin` on the `bird` object to give it the `glide` method.

```js
assert(typeof bird.glide === 'function');
```

Your code should use the `glideMixin` on the `boat` object to give it the `glide` method.

```js
assert(typeof boat.glide === 'function');
```

# --seed--

## --seed-contents--

```js
let bird = {
  name: "Donald",
  numLegs: 2
};

let boat = {
  name: "Warrior",
  type: "race-boat"
};

// Only change code below this line
```

# --solutions--

```js
let bird = {
  name: "Donald",
  numLegs: 2
};

let boat = {
  name: "Warrior",
  type: "race-boat"
};
function glideMixin (obj) {
  obj.glide = () => 'Gliding!';
}

glideMixin(bird);
glideMixin(boat);
```