How come animal become a supertype to dog and cat here. not even defined anywhere in code (like using constructor)

type or paste code here

 function Dog ( ) { }

Dog.prototype {
constructor: Animal,

Though dog’s protype must be initialized with constructor: Dog, else constructor property will fail (instance of works ,still). Help me understand this. Break and give detailed explanation. God bless.

look at following challenges, here there is not yet the connection of Cat to Animal