inventory.js

class InventoryObject {
  /**
   * @param {string} name
   * @param {number} price
   */
  constructor(name, price) {
    this.name = name;
    this.price = price;
  }

  /**
   * Return a discounted price without altering the object.
   * @param {number} percent
   * @returns {number}
   */
  getDiscountedPrice(percent) {
    // We work with cents in order to avoid float division
    const priceInCents = this.price * 100
    return Math.round(priceInCents * (100 - percent)/100) / 100
  }
}


const Inventory = {
  '000001': new InventoryObject('Banana Slicer', 2.99),
  '000002': new InventoryObject('Three Wolves Tea Cozy', 14.95)
}


// Retrieve the price
console.log(Inventory['000001'].price)  // 2.69

// Retrieve a discounted price (e.g. ten percent off)
console.log(Inventory['000001'].getDiscountedPrice(10))  // 2.69

// Create a new inventory object from a discounted price
Inventory['000003'] = new InventoryObject('Bargain Banana Slicer', Inventory['000001'].getDiscountedPrice(10))
console.log(Inventory['000003'])  // InventoryObject { name: 'Bargain Banana Slicer', price: 2.69 }

// Reduce the price of Banana Slicer by 10%
Inventory['000001'].price = Inventory['000001'].getDiscountedPrice(10)
console.log(Inventory['000001'])  // InventoryObject { name: 'Banana Slicer', price: 2.69 }