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;
};

Animal.prototype.identify = function(){
  //"I am a Human with 2 legs."
  return 'I am a ' + this.name + 'with ' + this.legs + 'legs'; 
};


var Zoo = {
  init : function(animals){
    this.animals = animals;
  },
  
  //array.filter(callback[, thisObject])
  //because we have an array of Animal objects we can use filter
  //to return the count or(length of array) for those that are true
  //in our statement. Kind of like the map method...
  bipeds : function(){
      return this.animals.filter(function(animal){
        return animal.legs === 2;
      });
  }, 

  //quadrupeds go here
  quadrupeds : function(){
    return this.animals.filter(function(animal){
      return animal.legs === 3;
    });
  }

};

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