GildedRose kata (https://github.com/emilybache/GildedRose-Refactoring-Kata) solutions

gilded_rose_clean.js

class Item {
  constructor(name, sellIn, quality) {
    this.name = name;
    this.sellIn = sellIn;
    this.quality = quality;
  }
}

class Shop {
  legendaries = ["Sulfuras, Hand of Ragnaros"];
  ageing = ["Aged Brie"];
  ageing_and_expiring = ["Backstage passes to a TAFKAL80ETC concert"];
  conjured = "Conjured";
  constructor(items = []) {
    this.items = items;
  }
  //There is another solution which involves setting deltas for sellIn and quality and handling each category of items
  //This has the advantage of putting the legendary item in the same indent level/conditions as the others   
  updateQuality() {
    this.items.forEach((i) => {
      if (this.legendaries.includes(i.name)) {
        return; //It does not age nor lose quality
      }
      i.sellIn--;
      if (this.ageing.includes(i.name)) {
        if (i.sellIn <= 0) i.quality += 2;
      } else if (this.ageing_and_expiring.includes(i.name)) {
        if (i.sellIn <= 0) i.quality = 0;
        else if (i.sellIn <= 5) i.quality += 3;
        else if (i.sellIn < 10) i.quality += 2;
        else i.quality++;
        //La qualité augmente de 2 quand il reste 10 jours ou moins et de 3 quand il reste 5 jours ou moins, mais la qualité tombe à 0 après le concert.
      } else if (i.name.includes(this.conjured)) {
        i.quality -= 2;
      } else if (i.sellIn > 0) {
        i.quality--;
      } else {
        //if (i.sellIn <= 0)
        i.quality -= 2;
      }

      if (i.quality < 0) i.quality = 0;
      if (i.quality > 50) i.quality = 50;
    });
    return this.items;
  }
}
module.exports = {
  Item,
  Shop,
};

gilded_rose_strategy.js

class Item {
  constructor(name, sellIn, quality) {
    this.name = name;
    this.sellIn = sellIn;
    this.quality = quality;
  }
}

class ItemStrategy {
  handle(item) {
    return false;
  }
  updateQuality(item) {}
}

class DefaultItemStrategy extends ItemStrategy {
  handle(item) {
    return true;
  }
  updateQuality(item) {
    item.sellIn--;
    if (item.sellIn > 0) {
      item.quality--;
    } else {
      item.quality -= 2;
    }

    if (item.quality < 0) item.quality = 0;
    if (item.quality > 50) item.quality = 50;
  }
}

class LegendaryItemStrategy extends ItemStrategy {
  handle(item) {
    return item.name == "Sulfuras, Hand of Ragnaros";
  }
}

class AgeingStrategy extends ItemStrategy {
  handle(item) {
    return item.name === "Aged Brie";
  }
  updateQuality(item) {
    item.sellIn--;
    if (item.sellIn > 0) item.quality++;
    if (item.sellIn <= 0) item.quality += 2;

    if (item.quality < 0) item.quality = 0;
    if (item.quality > 50) item.quality = 50;
  }
}
class AgeingAndExpiringStrategy extends ItemStrategy {
  handle(item) {
    return item.name === "Backstage passes to a TAFKAL80ETC concert";
  }
  updateQuality(item) {
    item.sellIn--;
    if (item.sellIn <= 0) item.quality = 0;
    else if (item.sellIn <= 5) item.quality += 3;
    else if (item.sellIn < 10) item.quality += 2;
    else item.quality++;

    if (item.quality < 0) item.quality = 0;
    if (item.quality > 50) item.quality = 50;
  }
}
class ConjuredStrategy extends ItemStrategy {
  handle(item) {
    return item.name.includes("Conjured");
  }
  updateQuality(item) {
    item.sellIn--;
    item.quality -= 2;
    if (item.quality < 0) item.quality = 0;
    if (item.quality > 50) item.quality = 50;
  }
}
class Shop {
  strategies = [
    new LegendaryItemStrategy(),
    new AgeingStrategy(),
    new AgeingAndExpiringStrategy(),
    new ConjuredStrategy(),
    new DefaultItemStrategy(),
  ];
  constructor(items = []) {
    this.items = items;
  }

  updateQuality() {
    this.items.forEach((i) => {
      for (let s of this.strategies)
        if (s.handle(i)) {
          s.updateQuality(i);
          break;
        }
    });
    return this.items;
  }
}
module.exports = {
  Item,
  Shop,
};