diff --git a/js/spec/gilded_rose_spec.js b/js/spec/gilded_rose_spec.js
index 44c3838b..86490977 100644
--- a/js/spec/gilded_rose_spec.js
+++ b/js/spec/gilded_rose_spec.js
@@ -1,9 +1,115 @@
-describe("Gilded Rose", function() {
+describe('Gilded Rose', function() {
 
-  it("should foo", function() {
-    const gildedRose = new Shop([ new Item("foo", 0, 0) ]);
-    const items = gildedRose.updateQuality();
-    expect(items[0].name).toEqual("fixme");
-  });
+  describe('with default item', function() {
+    const item = new Item('foo', 0, 0)
+    const items = [item]
+    const gildedRose = new Shop([item])
 
-});
+    it('has foo item', function() {
+      expect(items[0].name).toEqual('foo')
+    })
+
+    it('has foo item with 0 sellIn', function() {
+      expect(items[0].sellIn).toEqual(0)
+    })
+
+    it('has foo item with 0 quality', function() {
+      expect(items[0].quality).toEqual(0)
+    })
+  })
+
+  describe('#downgradeQuality', function() {
+    const item = new Item('foo', 10, 20)
+    const items = [item]
+    const gildedRose = new Shop([item])
+
+    it('downgrade quality by 1', function() {
+      gildedRose.downgradeQuality(items[0])
+
+      expect(items[0].quality).toEqual(19)
+    })
+
+    it('downgrade quality by 5', function() {
+      gildedRose.downgradeQuality(items[0], 5)
+
+      expect(items[0].quality).toEqual(14)
+    })
+  })
+
+  describe('#upgradeQuality', function() {
+    const item = new Item('foo', 10, 20)
+    const items = [item]
+    const gildedRose = new Shop([item])
+
+    it('upgrade quality by 1', function() {
+      gildedRose.upgradeQuality(items[0])
+
+      expect(items[0].quality).toEqual(21)
+    })
+
+    it('upgrade quality by 5', function() {
+      gildedRose.upgradeQuality(items[0], 5)
+
+      expect(items[0].quality).toEqual(26)
+    })
+  })
+
+  describe('#downgradeSellIn', function() {
+    const item = new Item('foo', 10, 20)
+    const items = [item]
+    const gildedRose = new Shop([item])
+
+    it('downgrade quality by 1', function() {
+      gildedRose.downgradeSellIn(items[0])
+
+      expect(items[0].sellIn).toEqual(9)
+    })
+
+    it('downgrade quality by 5', function() {
+      gildedRose.downgradeSellIn(items[0], 5)
+
+      expect(items[0].sellIn).toEqual(4)
+    })
+  })
+
+  describe('#hasQuality', function() {
+    const item = new Item('foo', 10, 20)
+    const items = [item]
+    const gildedRose = new Shop([item])
+
+    it('has quality', function() {
+      const hasQuality = gildedRose.hasQuality(items[0])
+
+      expect(hasQuality).toEqual(true)
+    })
+  })
+
+  describe('#commonQuality', function() {
+    const item = new Item('foo', 10, 20)
+    const items = [item]
+    const gildedRose = new Shop([item])
+
+    it('is a common quality', function() {
+      const commonQuality = gildedRose.commonQuality(items[0])
+
+      expect(commonQuality).toEqual(true)
+    })
+  })
+
+  describe('after updateQuality', function() {
+    const item = new Item('foo', 10, 20)
+    const items = [item]
+    const gildedRose = new Shop([item])
+    gildedRose.updateQuality()
+
+    it('has a good quality value', function() {
+      expect(items[0].quality).toEqual(19)
+    })
+
+    it('has a good sell in value', function() {
+      expect(items[0].sellIn).toEqual(9)
+    })
+
+    // TODO: Add custom tests with custom names, etc.
+  })
+})
diff --git a/js/src/gilded_rose.js b/js/src/gilded_rose.js
index 5358125e..d593543c 100644
--- a/js/src/gilded_rose.js
+++ b/js/src/gilded_rose.js
@@ -1,62 +1,83 @@
 class Item {
-  constructor(name, sellIn, quality){
-    this.name = name;
-    this.sellIn = sellIn;
-    this.quality = quality;
+  constructor(name, sellIn, quality) {
+    this.name = name
+    this.sellIn = sellIn
+    this.quality = quality
   }
 }
 
 class Shop {
-  constructor(items=[]){
-    this.items = items;
+  constructor(items = []) {
+    this.items = items
   }
-  updateQuality() {
-    for (var i = 0; i < this.items.length; i++) {
-      if (this.items[i].name != 'Aged Brie' && this.items[i].name != 'Backstage passes to a TAFKAL80ETC concert') {
-        if (this.items[i].quality > 0) {
-          if (this.items[i].name != 'Sulfuras, Hand of Ragnaros') {
-            this.items[i].quality = this.items[i].quality - 1;
-          }
-        }
-      } else {
-        if (this.items[i].quality < 50) {
-          this.items[i].quality = this.items[i].quality + 1;
-          if (this.items[i].name == 'Backstage passes to a TAFKAL80ETC concert') {
-            if (this.items[i].sellIn < 11) {
-              if (this.items[i].quality < 50) {
-                this.items[i].quality = this.items[i].quality + 1;
-              }
-            }
-            if (this.items[i].sellIn < 6) {
-              if (this.items[i].quality < 50) {
-                this.items[i].quality = this.items[i].quality + 1;
-              }
-            }
-          }
-        }
-      }
-      if (this.items[i].name != 'Sulfuras, Hand of Ragnaros') {
-        this.items[i].sellIn = this.items[i].sellIn - 1;
-      }
-      if (this.items[i].sellIn < 0) {
-        if (this.items[i].name != 'Aged Brie') {
-          if (this.items[i].name != 'Backstage passes to a TAFKAL80ETC concert') {
-            if (this.items[i].quality > 0) {
-              if (this.items[i].name != 'Sulfuras, Hand of Ragnaros') {
-                this.items[i].quality = this.items[i].quality - 1;
-              }
-            }
-          } else {
-            this.items[i].quality = this.items[i].quality - this.items[i].quality;
-          }
-        } else {
-          if (this.items[i].quality < 50) {
-            this.items[i].quality = this.items[i].quality + 1;
-          }
-        }
-      }
-    }
 
-    return this.items;
+  downgradeQuality(item, value = 1) {
+    item.quality -= value
+  }
+
+  upgradeQuality(item, value = 1) {
+    item.quality += value
+  }
+
+  downgradeSellIn(item, value = 1) {
+    item.sellIn -= value
+  }
+
+  hasQuality(item) {
+    return item.quality > 0
+  }
+
+  commonQuality(item) {
+    return item.quality < 50
+  }
+
+  updateQuality() {
+    this.items.map((item, i) => {
+
+      if (
+        $.inArray(item.name, [
+          'Aged Brie',
+          'Backstage passes to a TAFKAL80ETC concert',
+          'Sulfuras, Hand of Ragnaros',
+        ]) == -1 && this.hasQuality(item)
+      ) {
+        this.downgradeQuality(item)
+      }
+
+      else {
+        if (this.commonQuality(item)) {
+          this.upgradeQuality(item)
+
+          if (item.name == 'Backstage passes to a TAFKAL80ETC concert') {
+            if (item.sellIn < 11 && this.commonQuality(item))
+              this.upgradeQuality(item)
+
+            if (item.sellIn < 6 && this.commonQuality(item))
+              this.upgradeQuality(item)
+          }
+        }
+      }
+
+      if (item.name != 'Sulfuras, Hand of Ragnaros') this.downgradeSellIn(item)
+
+      if (item.sellIn < 0) {
+        if (item.name != 'Aged Brie') {
+          if (item.name != 'Backstage passes to a TAFKAL80ETC concert') {
+            if (item.name != 'Sulfuras, Hand of Ragnaros' &&
+                this.hasQuality(item))
+              this.downgradeQuality(item)
+          }
+          else {
+            this.downgradeQuality(item, item.quality)
+          }
+        }
+        else if (this.commonQuality(item)) {
+          this.upgradeQuality(item)
+        }
+      }
+
+    })
+
+    return this.items
   }
 }