How to update document and sub documents with nodejs?

[John]

My Entities with sub documents in MongoDB

@Entity()
@Unique(["orderNumber"])
export class Orders {
  @ObjectIdColumn()
  id: ObjectID;
  @Column()
  @Length(4, 10)
  orderNumber: string;
  @Column(type => Product)
  product: Product[];
  @Column()
  @Length(1, 50)
  totalAmount: string;
  @ObjectIdColumn()
  dealerId: ObjectID;
  @ObjectIdColumn()
  employeeid: ObjectID;
  @Column()
  @CreateDateColumn()
  createdAt: Date;
  @Column()
  @UpdateDateColumn()
  updatedAt: Date;
  order: Product;
}

@Entity()
export class Product {
  @PrimaryColumn()
  name: string;
  @Column()
  quantity: string;
  @Column()
  productAmount: string;
  constructor(name: string, quantity: string, productAmount: string) {
    this.name = name;
    this.quantity = quantity;
    this.productAmount = productAmount;
  }
}

---

NodeJs class to update

static editOrder = async (req: Request, res: Response, next: NextFunction) => {
const id = req.params.id;
const letAllProducts = req.body;
let { totalAmount, dealerId } = req.body;

const productRepository = getRepository(Product);
const orderRepository = getRepository(Orders);
let order: Orders;
try {
  await orderRepository.findOneOrFail(id);
} catch (error) {
  res.status(404).send("Order not found");
  return;
}
order.product = [];
for (let i of letAllProducts.product) {
  order.product.push(new Product(i.name, i.quantity, i.productAmount));
};
order.totalAmount = totalAmount; order.dealerId = ObjectId(dealerId);
const errors = await validate(order);
if (errors.length > 0) {
  res.status(400).send(errors);
  return;
}
try {
  await orderRepository.save(order);
} catch (e) {
  res.send(e);
  return;
}
res.status(200).send("Order updated successfully");

};

UnhandledPromiseRejectionWarning: TypeError: Cannot set property 'product' of undefined!

ps: i am noob. new to coading. Help much appreciated