text: class Product {
      constructor(name, price, num, specifications, notes) {
          this.id = "",
          this.name = name,
          this.price = Number(price),
          this.num = Number(num),
          this.specifications = specifications,
          this.notes = notes
      }
  }
  
  class User {
      constructor(name, tel, address, notes) {
          this.id = "",
          this.name = name,
          this.tel = tel,
          this.address = address,
          this.notes = notes
      }
  }
  
  class ProductOperation {
      constructor(product, salePrice, num) {
          this.id = "",
          this.product = product,
          this.salePrice = salePrice,
          this.num = num
      }
  }
  
  class PurchaseOrder {
      constructor(productOperations) {
          this.id = "",
          this.time = "",
          this.state = "",
          this.purchaseOperations = productOperations
      }
  }
  
  class SaleOrder {
      constructor(user, selling, productOperations, checkOuts) {
          this.id = "",
          this.time = "",
          this.state = "",
          this.user = user,
          this.selling = selling,
          this.saleOperations = productOperations,
          this.checkOuts = checkOuts
      }
  }
  
  class CheckOut {
      constructor(amount) {
          this.id = "",
          this.time = "",
          this.amount = amount
      }
  }
  