The Gilded Rose JavaScript

A Refactoring Kata

Adding a new feature to a giant unwieldy function with no tests in JavaScript. Yikes!

Approach

Tackled this across four branches -

• Spike: Start by digging into how the feature works and retrofitting tests to give confidence when making changes
• Spike2: Add the new feature requirement to existing code, with tests
• Refactor: Isolate an aspect of the functionality, abstracting the logic out and refactoring with tests (repeat)
• Tidy: Finalise test suite so every feature is tested across every requirement (tidy branch then merged back into master upon completion)

Spec

Hi and welcome to team Gilded Rose.

As you know, we are a small inn with a prime location in a prominent city ran by a friendly innkeeper named Allison. We also buy and sell only the finest goods. Unfortunately, our goods are constantly degrading in quality as they approach their sell by date.

We have a system in place that updates our inventory for us. It was developed by a no-nonsense type named Leeroy, who has moved on to new adventures. Your task is to add the new feature to our system so that we can begin selling a new category of items.

First an introduction to our system:

• All items have a sell_in value which denotes the number of days we have to sell the item

• All items have a quality value which denotes how valuable the item is

• At the end of each day our system lowers both values for every item

Pretty simple, right? Well this is where it gets interesting:

• Once the sell_in days is less then zero, quality degrades twice as fast

• The quality of an item is never negative

• "Aged Brie" actually increases in quality the older it gets

• The quality of an item is never more than 50

• "Sulfuras", being a legendary item, never has to be sold nor does it decrease in quality

• "Backstage passes", like aged brie, increases in quality as it's sell_in value decreases; quality increases by 2 when there are 10 days or less and by 3 when there are 5 days or less but quality drops to 0 after the concert

We have recently signed a supplier of conjured items. This requires an update to our system:

• "Conjured" items degrade in quality twice as fast as normal items

Feel free to make any changes to the update_quality method and add any new code as long as everything still works correctly. However, do not alter the Item class or items property as those belong to the goblin in the corner who will insta-rage and one-shot you as he doesn't believe in shared code ownership.

Just for clarification, an item can never have its quality increase above 50, however "Sulfuras" is a legendary item and as such its quality is 80 and it never alters.

Sources: http://iamnotmyself.com/2011/02/13/refactor-this-the-gilded-rose-kata/ https://github.com/professor/GildedRose

Starting Files

If you want to try it the starting files are in the root of the directory. Fork the repo and delete the Gilded Rose in the src to start over.

TL;DR (Spoilers)

There's lots of ways to tackle this. Mine went from...

export default function update_quality() {
  for (var i = 0; i < items.length; i++) {
    if (items[i].name != 'Aged Brie' && items[i].name != 'Backstage passes to a TAFKAL80ETC concert') {
      if (items[i].quality > 0) {
        if (items[i].name != 'Sulfuras, Hand of Ragnaros') {
          items[i].quality = items[i].quality - 1
        }
      }
    } else {
      if (items[i].quality < 50) {
        items[i].quality = items[i].quality + 1
        if (items[i].name == 'Backstage passes to a TAFKAL80ETC concert') {
          if (items[i].sell_in < 11) {
            if (items[i].quality < 50) {
              items[i].quality = items[i].quality + 1
            }
          }
          if (items[i].sell_in < 6) {
            if (items[i].quality < 50) {
              items[i].quality = items[i].quality + 1
            }
          }
        }
      }
    }
    if (items[i].name != 'Sulfuras, Hand of Ragnaros') {
      items[i].sell_in = items[i].sell_in - 1;
    }
    if (items[i].sell_in < 0) {
      if (items[i].name != 'Aged Brie') {
        if (items[i].name != 'Backstage passes to a TAFKAL80ETC concert') {
          if (items[i].quality > 0) {
            if (items[i].name != 'Sulfuras, Hand of Ragnaros') {
              items[i].quality = items[i].quality - 1
            }
          }
        } else {
          items[i].quality = items[i].quality - items[i].quality
        }
      } else {
        if (items[i].quality < 50) {
          items[i].quality = items[i].quality + 1
        }
      }
    }
  }
}

to...

export default function update_quality(items = []) {
  for (var i = 0; i < items.length; i++) {
    if (items[i].name === 'Sulfuras, Hand of Ragnaros') {
      return update_sulfuras(items[i]);
    }

    items[i].sell_in--;

    if (items[i].name === 'Aged Brie') {
      return update_brie(items[i]);
    }
    if (items[i].name === 'Backstage passes to a TAFKAL80ETC concert') {
      return update_backstage_pass(items[i]);
    }

    if (items[i].name === 'Conjured Mana Cake') {
      return update_conjured(items[i]);
    }
    return update_regular_item(items[i]);
  }
}