export class OrderItem { id!: number; quantity!: number; unitPrice!: number; productId!: number; productSize!: string; productTitle!: string; productArtist!: string; productArtId!: string; productCategory!: string; } export class Order { orderId!: number; orderDate: Date = new Date(); orderNumber: string = Math.random().toString(36).substr(2,5); items: OrderItem[] = []; get subtotal(): number { const result = this.items.reduce( (tot, val) => { return tot + (val.unitPrice * val.quantity); }, 0); return result; } }