good-birds.js

class Bird {
  layEgg () {}
}

class FlyingBird {
  fly () {}
}

class SwimmingBird extends Bird {
  swim () {}
}

class Eagle extends FlyingBird {}

class Penguin extends SwimmingBird {}

const penguin = new Penguin();
penguin.swim();
penguin.layEgg();

const eagle = new Eagle();
eagle.fly();
eagle.layEgg();

Hey there 👋

Shouldn't the Penguin class learn to swim? :D

class Penguin extends SwimmingBird {}

Hey @sitek94

Lol, you are 100% correct Idk what I was thinking, haha.
I went ahead and updated it thanks for pointing that out.

We need intellisense when writing gists haha :D

By the way, thanks for really helpful examples :)

line 23: eagle.layEgg(); <== how is that even possible since class Eagle extends FlyingBird {} and FlyingBird class does not extend Bird ?

I think so too. It seems on line 5 it should have been like this:

class FlyingBird extends Bird {