How to get Readable error response from JavaScript Fetch API?

透過 fetch 取得 server side 回傳的 json 之外, 如何處理伺服器回傳的錯誤代碼. 參考看看:

How to get Readable error response from JavaScript Fetch API?
https://stackoverflow.com/questions/40408219/how-to-get-readable-error-response-from-javascript-fetch-api

Check here https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch

fetch(deafaultUrl + '/v1/users/',
            {
                headers: {
                    'Accept': 'application/json',
                    'Content-Type': 'application/json'
                },
                method: "POST",
                body: JSON.stringify(userInfoParams)
            })
            .then(function(response) {
                console.log(response);
                console.log(response.body);
                console.log(response.message);
                console.log(response.errors);
                console.log(response.json());
                dispatch(update_errors(response));

                if (response.status >= 400) {
                    throw new Error("Bad response from server");
                }

            })
            .then(function(json){
                console.log("succeed json re");
                // We can dispatch many times!
                // Here, we update the app state with the results of the API call.

                dispatch(update_user(json));

            })
            // here's the way to access the error message
            .catch(function(error) {
              console.log(error.response.data.message)
            })

使用 response.status 可以拿到http 的 status code.

response.json() 可以拿到 json 內容. 但只能使用 .json() 一次,