Basics of prototype chaining and hierarchy

prototypes.js

function Animal (animalName) {
  this.name = animalName
}

Animal.prototype.walk = function () {
  console.log('Walking around...')
}

function Cat (catName) {
  Animal.call(this, catName)
  this.type = 'cat'
}
Cat.prototype = new Animal()
Cat.prototype.scratch = function () {
  console.log('Scratching your forniture...')
}

var meow  = new Animal('Meow')
var shell = new Cat('Shell')

shell.walk()
shell.scratch()