prototype chain

prototype_chain.js

function Animal(name) {
    this.name = name;
}
Animal.prototype = {
    weight: 0,
    eat: function() {
        console.log("Animal is eating!");
    }
}

function Mammal() {
    this.name = "mammal";
}
Mammal.prototype = new Animal("animal");

function Horse(height, weight) {
    this.name = "horse";
    this.height = height;
    this.weight = weight;
}
Horse.prototype = new Mammal();
Horse.prototype.eat = function() {
    console.log("Horse is eating grass!");
}

var horse = new Horse(100, 300);
console.log(horse.__proto__ === Horse.prototype);
console.log(Horse.prototype.__proto__ === Mammal.prototype);
console.log(Mammal.prototype.__proto__ === Animal.prototype);