是否有跨域问题
Access to XMLHttpRequest at 'http://localhost:3000/xxx' from origin 'http://localhost:8081' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. 控制台显示这个错误,不能打印出res,但是response返回结果里显示有数据。 这个怎么解决呢