问如何修复Node.js/mysql cart应用程序中的“app GET /add_ to _cart/”

EN

<p><a href="/add_to_cart/<%=this.id%>" class="btn btn-primary" role="add">Add to cart</a></p>

router.get('/add_to_cart/:id', (req, res)=> {
  //check if cart has an object otherwise pass empty object
  const productID = req.params.id;
  console.log(productID);
  const cart = new Cart(req.session.cart ? req.session.cart : {});

  //mysql statement find product by // ID
  let sql ="SELECT * FROM products WHERE id = ? LIMIT 1";
  let query = db.query(sql, id, (err, result)=>{
      if(err) throw err;
      console.log(result);
      if(result.length){
        cart.add(product, product.id);
        req.session.cart;
        console.log(req.session.cart);
        res.redirect("/");
      }

  });
});