Override Inherited Methods

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

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

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

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:

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.

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