zoo.js

//------------------------------------------------------------------------------------------------------------------
// YOUR CODE: Create your Zoo "object literal" and Animal "constructor" and "prototypes" here.
//------------------------------------------------------------------------------------------------------------------

function Animal(name, legNum){
  this.name = name;
  this.legNum = legNum;
} 

// if something is a function then you can define prototype for it

// var a1 = new Animal("Human", 2);

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

// ... is the same as ...

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

// var a2 = new Animal("Bear", 4);


// var a = new Animal("Human", 2);
// a.identify = function() {}
// var b = new Animal("Bird", 2);
// b.identify() // error!

// Animal is a function (used as a constructor-style object)
// when we want to assign properties to the obj, then we need 'this'

var Zoo = {
  zooAnimals: [],
  init: function(animals){
    for(i=0; i< animals.length; i++){
      this.zooAnimals.push(animals[i])
    }
  },

  categorize: function(legNum){
    category = [] 
    for(i=0; i< this.zooAnimals.length; i++){
      if (this.zooAnimals[i].legNum === legNum) {
        category.push(this.zooAnimals[i])
      }
    }
    return category
  },

  bipeds: function(){ return this.categorize(2) },
  quadrupeds: function(){ return this.categorize(4) }

}

// Zoo is an obj literal, not a contructor

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