guilded_rose.js

function Item(name, sell_in, quality) {
  this.name = name;
  this.sell_in = sell_in;
  this.quality = quality;
}

var items = []

var DEXTERITY_VEST = "+5 Dexterity Vest";
var AGED_BRIE = "Aged Brie";
var ELIXIR = "Elixir of the Mongoose";
var SULFURAS = "Sulfuras, Hand of Ragnaros";
var BACKSTAGE_PASSES = "Backstage passes to a TAFKAL80ETC concert";
var CAKE = "Conjured Mana Cake";

var MAX_QUALITY = 50;
var MIN_QUALITY = 0;

items.push(new Item(DEXTERITY_VEST, 10, 20));
items.push(new Item(AGED_BRIE, 2, 0));
items.push(new Item(ELIXIR, 5, 7));
items.push(new Item(SULFURAS, 0, 80));
items.push(new Item(BACKSTAGE_PASSES, 15, 20));
items.push(new Item(CAKE, 3, 6));

function update_quality() {
  for (var i = 0; i < items.length; i++) {

    if(item_is_sulfuras(items[i])) {
      continue;
    }

    advance_time(i);

    if(items[i].name === BACKSTAGE_PASSES){
      update_backstage_passes(items[i], i);
      continue;
    }

    if (item_is_generic(items[i])) {
      decrease_generic_quality(i);
    } else {
      increase_rare_quality(i)
    }

    if (items[i].sell_in < 0) {
      if(item_is_generic(items[i])) {
        decrease_generic_quality(i);
      } else {
        increase_rare_quality(i);
      }
    }
  }
}

var update_backstage_passes = function(item, i){
  if(item.sell_in < 0) {
    item.quality = MIN_QUALITY;
  } else if(item.sell_in < 5) {
    increase_quality(i, 3);
  } else if (item.sell_in < 10) {
    increase_quality(i, 2);
  } else {
    increase_quality(i, 1);
  }
}

var item_is_generic = function(item) {
  return item.name != AGED_BRIE && item.name != BACKSTAGE_PASSES;
}

var item_is_sulfuras = function(item) {
  return item.name == SULFURAS;
}

var decrease_generic_quality = function(i){
  if (items[i].quality > MIN_QUALITY) {
    items[i].quality = items[i].quality - 1
  }
}
var advance_time = function(i){
  items[i].sell_in = items[i].sell_in - 1;
}

var increase_rare_quality = function(i){
  if (items[i].quality < MAX_QUALITY) {
    increase_quality(i, 1);
  }
}

var increase_quality = function(i, factor) {
  items[i].quality = items[i].quality + factor;
}

guilded_rose_spec.js

describe("Gilded Rose", function() {
  beforeEach(function(){
    items = []

    items.push(new Item('+5 Dexterity Vest', 10, 20));
    items.push(new Item('Aged Brie', 2, 0));
    items.push(new Item('Elixir of the Mongoose', 5, 7));
    items.push(new Item('Sulfuras, Hand of Ragnaros', 0, 80));
    items.push(new Item('Backstage passes to a TAFKAL80ETC concert', 15, 20));
    items.push(new Item('Conjured Mana Cake', 3, 6));
  })
describe("items", function(){
  it("should have a sell_in value", function(){
    expect(items[0].sell_in).toBe(10);
  });

  it("should have a quality value", function(){
    expect(items[0].quality).toBe(20);
  });

});
describe("update quality", function(){

  it("sell_in date for generic items decreases one at the end of the day", function() {
    update_quality()
    expect(items[0].sell_in).toBe(9);
  });

  it("an item's quality should never be negative", function(){
    for (var i = 0; i < 8; i++ ){
      update_quality();
    }
    expect(items[2].quality).toBe(0);
  });

  it("Aged Brie increases in quality over time", function(){
    update_quality();
    expect(items[1].quality).toBe(1);
  });


  it("a generic item's quality should never exceed 50", function(){
    for (var i = 0; i < 51; i++) {
      update_quality();
    }
    expect(items[1].quality).toBe(50);
  });

  it("Sulfuras's sell_in value never decreases", function(){
    update_quality();
    expect(items[3].sell_in).toBe(0);
  });

  it("Sulfuras's quality never alters", function(){
    update_quality();
    expect(items[3].quality).toBe(80);
  });

  it("Backstage passes increase in quality as sell_in value decreases", function(){
    update_quality();
    expect(items[4].quality).toBe(21);
  });

   it("Backstage passes increase in quality twice as fast if sell_in is less than 10", function(){
    for (var i = 0; i < 6; i++){
      update_quality();
    }
    expect(items[4].quality).toBe(27);
  });

  it("Backstage passes increase in quality thrice as fast if sell_in is less than 5", function(){
    for (var i = 0; i < 11; i++){
      update_quality();
    }
    expect(items[4].quality).toBe(38);
  });

  it("Backstage passes quality drops to 0 when the sell_in date is 0", function(){
    for (var i = 0; i < 16; i++){
      update_quality();
    }
    expect(items[4].quality).toBe(0);
  });
});


});