freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/object-oriented-programming/override-inherited-methods.md

---
id: 587d7db1367417b2b2512b88
title: Override Inherited Methods
challengeType: 1
forumTopicId: 301322
dashedName: override-inherited-methods
---

# --description--

In previous lessons, you learned that an object can inherit its behavior (methods) from another object by referencing its `prototype` object:

```js
ChildObject.prototype = Object.create(ParentObject.prototype);
```

Then the `ChildObject` received its own methods by chaining them onto its `prototype`:

```js
ChildObject.prototype.methodName = function() {...};
```

It's possible to override an inherited method. It's done the same way - by adding a method to `ChildObject.prototype` using the same method name as the one to override. Here's an example of `Bird` overriding the `eat()` method inherited from `Animal`:

```js
function Animal() { }
Animal.prototype.eat = function() {
  return "nom nom nom";
};
function Bird() { }

Bird.prototype = Object.create(Animal.prototype);

Bird.prototype.eat = function() {
  return "peck peck peck";
};
```

If you have an instance `let duck = new Bird();` and you call `duck.eat()`, this is how JavaScript looks for the method on the `prototype` chain of `duck`:

1.  `duck` => Is `eat()` defined here? No.
2.  `Bird` => Is `eat()` defined here? => Yes. Execute it and stop searching.
3.  `Animal` => `eat()` is also defined, but JavaScript stopped searching before reaching this level.
4.  Object => JavaScript stopped searching before reaching this level.

# --instructions--

Override the `fly()` method for `Penguin` so that it returns the string `Alas, this is a flightless bird.`

# --hints--

`penguin.fly()` should return the string `Alas, this is a flightless bird.`

```js
assert(penguin.fly() === 'Alas, this is a flightless bird.');
```

The `bird.fly()` method should return the string `I am flying!`

```js
assert(new Bird().fly() === 'I am flying!');
```

# --seed--

## --seed-contents--

```js
function Bird() { }

Bird.prototype.fly = function() { return "I am flying!"; };

function Penguin() { }
Penguin.prototype = Object.create(Bird.prototype);
Penguin.prototype.constructor = Penguin;

// Only change code below this line



// Only change code above this line

let penguin = new Penguin();
console.log(penguin.fly());
```

# --solutions--

```js
function Bird() { }

Bird.prototype.fly = function() { return "I am flying!"; };

function Penguin() { }
Penguin.prototype = Object.create(Bird.prototype);
Penguin.prototype.constructor = Penguin;
Penguin.prototype.fly = () => 'Alas, this is a flightless bird.';
let penguin = new Penguin();
console.log(penguin.fly());
```