$.post("/shop/cart/update",{product_id : productid, add_qty : 1, set_qty : 0})

    @http.route(['/shop/cart/update'], type='http', auth="public", methods=['POST'], website=True)
    def cart_update(self, product_id, add_qty=1, set_qty=0, **kw):
        cr, uid, context = request.cr, request.uid, request.context
        request.website.sale_get_order(force_create=1)._cart_update(product_id=int(product_id), add_qty=float(add_qty), set_qty=float(set_qty))
        return request.redirect("/shop/cart")