zoo.js

//------------------------------------------------------------------------------------------------------------------
// YOUR CODE: Create your Zoo "object literal" and Animal "constructor" and "prototypes" here.
//------------------------------------------------------------------------------------------------------------------
function Animal(name, legs)
{
  this.name = name;
  this.legs = legs;
  // this is a method that gets created every time a new Animal is created
  // this.bar = function() {

  // };
};

// this method is shared among all instances of Animal
Animal.prototype.identify = function() {
  return "I am a " + this.name + " with " + this.legs + " legs."
};

// These are the ruby equivalents
// PROTOTYPE:
// class String
//   def foo
//     to_s + "!!!!"
//   end
// end

// CONSTRUCTOR:
// s = "hi, bill"
// def s.bar
//   to_s + "????"
// end

var Zoo = {
  init: function(animals) {
    this.animals = animals;
  },

  bipeds: function () {
    return this.animals.filter(function(animal) {
      return animal.legs === 2;
    });
  },

  quadrupeds: function () {
    return this.animals.filter(function(animal) {
      return animal.legs === 4;
    });
  }


}

//------------------------------------------------------------------------------------------------------------------
// DRIVER CODE: Do **NOT** change anything below this point. Your task is to implement code above to make this work.
//------------------------------------------------------------------------------------------------------------------

function assert(test, message) {  
  if (!test) {
    throw "ERROR: " + message;
  }
  return true;
}

var animals = [
  new Animal("Human", 2),
  new Animal("Monkey", 2),
  new Animal("Kangaroo", 2),
  new Animal("Horse", 4),
  new Animal("Cow", 4),
  new Animal("Centipede", 100)
];

Zoo.init(animals);

assert(
  Zoo.bipeds().length === 3, "the Zoo should have 3 bipeds"
);
assert(
  Zoo.quadrupeds().length === 2, "the Zoo should have 2 bipeds"
);
assert(
  animals[0].identify() === "I am a Human with 2 legs.", "humans have 2 legs"
);
assert(
  animals[2].name === "Kangaroo", "expected 'Kangaroo'"
);
assert(
  animals[0].identify === animals[5].identify, "only one implementation of the identify() function should exist"
);