dog.js

// *************************************
// FP
// *************************************
var Dog = function() {
    var weight = 15;
    var age = 1;
    return {
        feed : function(amount){
            weight += amount;
        },
        bark : function(){
            console.log("Bark! I weigh " + weight + " pounds!");
        }
    }
};

Shaggy = Dog();
Shaggy.feed(10);
Shaggy.bark();
// Bark! I weigh 25 pounds!

// *************************************
// OOP
// *************************************

var Dog = function() {
    this.weight = 15;
    this.age = 1;
};

Dog.prototype.feed = function(amount) {
    this.weight += amount;
};

Dog.prototype.bark = function() {
    console.log("Bark! I weigh " + this.weight + " pounds!");
};

Shaggy = new Dog();
Shaggy.feed(10);
Shaggy.bark();
// Bark! I weigh 25 pounds!