Thinking more...

一般是寫 .catch((err) => {console.log(err);}
這樣只會看到 http status 的錯誤，不能取得 response。那該怎麼取得 error response 呢？axios 文件有寫了，用 err.response: https://github.com/axios/axios#handling-errors

axios.get('/user/12345')
  .catch(function (error) {
    if (error.response) {
      // The request was made and the server responded with a status code
      // that falls out of the range of 2xx
      console.log(error.response.data);    // 取得內容，用 error.response.data
      console.log(error.response.status);  // 取得狀態碼，用 error.response.status
      console.log(error.response.headers); // 取得表頭，用 error.response.headers
    } else if (error.request) {
      // The request was made but no response was received
      // `error.request` is an instance of XMLHttpRequest in the browser and an instance of
      // http.ClientRequest in node.js
      console.log(error.request);
    } else {
      // Something happened in setting up the request that triggered an Error
      console.log('Error', error.message);
    }
    console.log(error.config);
  });