index.html

<script src="zoo.js"></script>

zoo.js

//------------------------------------------------------------------------------------------------------------------
// YOUR CODE: Create your Zoo "object literal" and Animal "constructor" and "prototypes" here.
//------------------------------------------------------------------------------------------------------------------
//---------------Zoo Code-------------------------------------
var Zoo = {}

Zoo.init = function(animals){
  this.animals = animals
}

Zoo.bipeds = function(){
  var bipeds = []
  for (var i=0; i < this.animals.length; i++)
  {
    if(this.animals[i].legs == 2){
      bipeds.push(animals[i])
    }
  }
  return bipeds;
}

Zoo.quadrupeds = function(){
  var quadrupeds = []
  for (var i=0; i < this.animals.length; i++)
  {
    if(this.animals[i].legs == 4){
      quadrupeds.push(animals[i])
    }
  }
  return quadrupeds;
}

//---------------Animal Code-------------------------------------
function Animal(name, legs){
  this.name = name;
  this.legs = legs;
}

Animal.prototype.identify = function(){
  return "I am a " + this.name + " with " + this.legs + " legs.";
}

Animal.prototype.name = function(){
  return this.name;
}

//------------------------------------------------------------------------------------------------------------------
// 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"
);