Private state

gistfile1.js

var @priv = {};

function Animal() {
  priv[this] = {};
  priv[this].walked = false;
}

Animal.prototype.walk = function walk() {
  console.log('walking...')
  priv[this].walked = true
}

Animal.prototype.hasBeenWalked = function hasBeenWalked() {
  return priv[this].walked
}

module.exports = Animal;