gistfile1.js

var Creature = (function () {
    // constructor
    function Creature (name) {
        // public properties
        this.name = name;
        this.extremities;
        this.isBird;
    }
    // private properties
    var bones;
    // public methods
    Creature.prototype.walk = function () {
        for (var i = 0; i < this.extremities; i++) {
            console.log(i+1+" leg ahead.");
        }
    }
    Creature.prototype.breathe = function () {
         _heartbeat();
    }
    Creature.prototype.fly = function () {
        console.log((!this.isBird) ? "Can't fly, just jump." : "Fly!")
    }
    Creature.prototype.eat = function (food) {
        console.log(this.name + " eats " + food)
    }
    // private methods
    function _heartbeat () {
        console.log("tap-tap-tap");
    }
    return Creature;
})();