Develop Reference

JavaScript-ReactJS problem with GET fetch request ReactJS

I'm trying to doing a basic GET request from ReactJS app to a Node.js API, but I'm getting a response with status 304. I need get a 200 status to save the response of GET in a variable. (Im running Reactjs app in port 3000 and Nodejs API in port 3300)
Node API:
app.get('/serviciosextras', async (req, res) => {
let connection;
console.log(('Servicios Extras'));
try {
connection = await oracledb.getConnection({
user: 'portafolio',
password: '123',
connectString: "localhost:1521/orcl"
});
const result = await connection.execute(
`SELECT dep.id_departamento,
se.id_servicio,
se.precio_servicio
FROM departamento_servicio_detalle dsd
JOIN departamento DEP ON (dsd.id_departamento = dep.id_departamento)
JOIN servicio_extra SE ON (dsd.id_servicio = se.id_servicio)
ORDER BY 1 ASC`
)
const resultSet = result.rows;
let lista = [];
resultSet.map(obj => {
let serviciosSchema = {
'id_departamento': obj[0],
'id_servicio': obj[1],
'precio_servicio': obj[2]
}
lista.push(serviciosSchema);
});
console.log(lista);
res.json(lista);
connection.close();
} catch (err) {
console.error(err);
}
});
GET request from Reactjs
const getExtraServices = () => {
let endpoint = `${URL}serviciosextras`;
const requestOptions = {
method: "GET",
mode: 'no-cors'
// headers: {
// "Content-Type": "application/json",
// Accept: "application/json"
// },
};
console.log(endpoint);
fetch(endpoint, requestOptions)
.then((res, err) => {
console.log(res);
})
.then(result => {
console.log('fue aqui');
console.log(result);
})
.catch(err => {
console.log('ERROR');
console.log(err);
})
}
Im calling the method from this button:(onClick={getExtraServices()})
<Fab onClick={(e) => {
e.preventDefault();
getExtraServices();
}} variant="extended">
<NavigationIcon style={{marginRight: 'theme.spacing(1)'}} />
Navigate
</Fab>
so... I'm getting this:
Firefox Console when I clicked button to call getExtraServices() res is undefined
Network console of GET request I got a response but the status is 304, so I can't get this from code. :/
Console of Nodejs API this console.log if from console.log(lista) before send the res.json(lista)
Does someone know how can I fix this? I need get the response of the GET request to charge a list in ReactJS app, but I can't because the response has body:null.

Error 304 isn't the problem.
It looks like you are missing a statement to turn your response into JSON.
Here's an example from MDN:
fetch('https://example.com/profile', {
method: 'POST', // or 'PUT'
headers: {
'Content-Type': 'application/json',
},
body: JSON.stringify(data),
})
.then(response => response.json())
.then(data => {
console.log('Success:', data);
})
.catch((error) => {
console.error('Error:', error);
});
In particular:
.then(response => response.json())
In your code:
fetch(endpoint, requestOptions)
.then((res, err) => {
console.log(res); // logging res
// no data being returned here
})
.then(result => {
console.log('fue aqui');
console.log(result); // therefore result is undefined
})
.catch(err => {
console.log('ERROR');
console.log(err);
})

axios transformResponse returning undefined

With the following I get the expected response.data value:
axios({
method,
url
}).then(response => { console.log(response) })
However, when I add the transformResponse property as follows I get a response.data value of undefined:
axios({
method,
url,
transformResponse: [(data) => {
return data
}]
}).then(response => { console.log(response) })
Can someone please tell me what I'm missing here! Thanks

I suggest you to use interceptors since they are more clean
Interceptors work as a middlware on your requests
remove transformResponse and add this
axios.interceptors.response.use(function (response) {
return response.data;
});
axios({
method,
url,
}).then(response => { console.log(response) })

You can check the below sample to safe parse. transformResponse get data as raw staring so u can parse it.
const instance = axios.create({
baseURL: baseURL,
transformResponse: [
(data) => {
let resp;
try {
resp = JSON.parse(data);
} catch (error) {
throw Error(
`[requestClient] Error parsingJSON data - ${JSON.stringify(
error
)}`
);
}
if (resp.status === "success") {
return resp.data;
} else {
throw Error(`Request failed with reason - ${data}`);
}
},
],
});
Else you can use an interceptor to simplify it.
//const axios = require("axios");
const jsonInterceptor = [
(response) => response.data,
(error) => Promise.reject(error),
];
function jsonClient() {
const client = axios.create();
client.interceptors.response.use(...jsonInterceptor);
return client;
}
// Page 1
const jhttp = jsonClient();
jhttp
.get("https://jsonplaceholder.typicode.com/todos/1")
.then((data) => console.log(data));
<script src="https://cdnjs.cloudflare.com/ajax/libs/axios/0.19.2/axios.min.js"></script>

For anyone wondering here is the response:
axios.get(url, {
headers: {
'Content-Type': 'application/json'
},
transformResponse: axios.defaults.transformResponse.concat((data) => {
console.log(data) // this should now be JSON
})
})
from https://github.com/axios/axios/issues/430#issuecomment-243481806

Trying to get data an 'status' from fetch Promise

I am trying to make a generic Fetch method for my React project. The plan is to pass my fetch method a url, and some config data (method, header etc). And then return less technical data to my calling methods. I'd like to return the data from the api call, and the payload, which is json data.
return fetch(URL, config)
.then((response) => {
console.log('Fetch - Got response: ', response);
return response;
})
.then((response) => {
console.log('Json: ', response.status);
const result = { data: response.json(), status: response.status };
return result;
})
.catch((e) => {
console.log(`An error has occured while calling the API. ${e}`);
reject(e);
});
This is my initial attempt, but I'm not quite sure what I'm doing.
my console log that logs 'response', contains the response from the API call:
body: (...)
bodyUsed: true
headers: Headers {}
ok: true
redirected: false
status: 200
statusText: "OK"
type: "cors"
url: "http://localhost:49487//api/xxx/yyy"
So the API call completes, and I get a 200 status.
The line:
console.log('Json: ', response.status);
return 200 as expected.
What I have been doing before is
return response.json()
And then my calling class gets the paylad, but no status. What I am trying to do is return my payload, AND the status.
So I attempted to change it to this:
const result = { data: response.json(), status: response.status };
return result;
But my calling app now sees:
data: Promise {<resolved>: Array(9)}
status: 200
I was expecting to get data: MyPayloadArray, status: 200
I think I'm misunderstanding promises here. (I'm quite green with them).
My data accessor that uses my Fetch method:
static GetAll() {
return new Promise((resolve, reject) => {
const request = {
method: 'GET',
URL: `${Server.ApiURL}/api/admin/clients`,
};
fetchData(request)
.then((result) => {
console.log('GetAll sees response as ', result);
resolve(result);
})
.catch((error) => {
reject(new Error(error));
});
});
}
I'm trying to call my data accessor class, like this:
componentDidMount() {
ClientDataAccessor.GetAll()
.then((response) => {
console.log('Got list!', response);
this.setState({ clients: response, isLoading: false });
})
.catch((error) => {
console.log('Got error on list screen', error);
});
}
How can I get just the status, and the payload back to my DataAccesor class? I think I'm just screwing up the Promises... But not sure of the best pattern here.
I'm going UI class, onComponentDidMount -> DataAccessor.GetAll -> FetchData. I think I'm abusing the Promise somewhere.

The issue here is that response.json() returns another promise. You would have to resolve that promise object yourself and return the object you are looking for.
return fetch(URL, config)
.then((response) => {
console.log('Fetch - Got response: ', response);
return response;
})
.then((response) =>
response.json()
.then( (data) => { data, status: response.status } )
)
.catch((e) => {
console.log(`An error has occured while calling the API. ${e}`);
reject(e);
});
Very ugly...
Why not move it to async/await funtion? All browsers support it at this stage...
async myFetch(URL, config) {
try {
const response = await fetch(URL, config);
console.log('Fetch - Got response:', response);
const data = await response.json();
console.log('Fetch - Got data:', data);
return { data, status: response.status }
}
catch (e) {
console.error(`An error has occured while calling the API. ${e}`);
throw e;
}
}
Just be aware, in both cases, that your function returns another promise.

I think you can solve your issue using Promise.resolve, chaining promise to obtain your result object:
...
.then(response => {
var status = response.status;
return Promise.resolve(response.json())
.then(data => ({ data, status }))
})
The Promise.resolve can take a Promise as parameter and return a promise that will flatten the chain, so you can get the value of the json parse and work with it.

You need to further resolve res.json() to get the info. You can do something like this:
return fetch(URL, config)
.then((response) => {
console.log('Fetch - Got response: ', response);
return response;
})
.then(response =>
response.json().then(json => ({
status: response.status,
json
})
))
.then(({ status, json }) => {
console.log({ status, json });
return { data: json, status: status };
})
.catch((e) => {
console.log(`An error has occured while calling the API. ${e}`);
reject(e);
});
The neat version of above could be:
return fetch(URL, config)
.then(response => response.json()
.then(json => ({ status: response.status, data: json }) )
)
Note: Removed the reject(e) from inside of catch, because it is redundant.

Fetch API error handling

I want to display error message from my API, problem is that I can't reach that error if I check for response.ok, it returns Fetch error, not the one from API..
If I don't use if(response.ok)... it returns the error from API but it dispatches the success action.
Here is the example, login action:
export const signIn = data => dispatch => {
dispatch({
type: SIGN_IN
})
fetch(API_URL+'/login', {
method: 'POST',
headers: {
'content-type': 'application/json'
},
body: JSON.stringify(data),
})
.then( response => {
if (!response.ok) { throw response }
return response.json() //we only get here if there is no error
})
.then( json => {
dispatch({
type: SIGN_IN_SUCCESS, payload: json
}),
localStorage.setItem("token", 'Bearer '+json.token)
localStorage.setItem("user", JSON.stringify(json.user))
})
.catch( err => {
dispatch({
type: SIGN_IN_FAILED, payload: err
})
})
}
This is the code for action that dispatches the right message but as success action, not as failed one..
export const signIn = data => dispatch => {
dispatch({
type: SIGN_IN
})
fetch(API_URL+'/login', {
method: 'POST',
headers: {
'content-type': 'application/json'
},
body: JSON.stringify(data),
})
.then( response => response.json())
.then( json => {
dispatch({
type: SIGN_IN_SUCCESS, payload: json
}),
localStorage.setItem("token", 'Bearer '+json.token)
localStorage.setItem("user", JSON.stringify(json.user))
})
.catch( err => {
dispatch({
type: SIGN_IN_FAILED, payload: err
})
})
}

With the following solution one can handle JSON API error, Generic API error and Generic fetch error
fetch("api/v1/demo", {
method: "POST",
headers: {
"Content-Type": "application/json"
},
body: JSON.stringify({
"data": "demo"
})
})
.then(response => {
if (!response.ok) {
return Promise.reject(response);
}
return response.json();
})
.then(data => {
console.log("Success");
console.log(data);
})
.catch(error => {
if (typeof error.json === "function") {
error.json().then(jsonError => {
console.log("Json error from API");
console.log(jsonError);
}).catch(genericError => {
console.log("Generic error from API");
console.log(error.statusText);
});
} else {
console.log("Fetch error");
console.log(error);
}
});

according to This Article :
Per MDN, the fetch() API only rejects a promise when
“a network
error is encountered, although this usually means permissions issues
or similar.”
Basically fetch() will only reject a promise if the user
is offline, or some unlikely networking error occurs, such a DNS
lookup failure.
then, you can use this part of code to use non-network error handlings and make your code more readable
function handleErrors(response) {
if (!response.ok) throw new Error(response.status);
return response;
}
fetch("API URL")
// handle network err/success
.then(handleErrors)
// use response of network on fetch Promise resolve
.then(response => console.log("ok") )
// handle fetch Promise error
.catch(error => console.log(error) );

In order to extract API message from server in case of some error, you have to use the following idiom (which doesn't lie on the surface though), see link
fetch("http://localhost:8090/test/error", {
method: 'GET',
headers: {
'Accept': 'application/json'
}
})
.then(result => {
//Here body is not ready yet, throw promise
if (!result.ok) throw result;
return result.json();
})
.then(result => {
//Successful request processing
console.log(result);
}).catch(error => {
//Here is still promise
console.log(error);
error.json().then((body) => {
//Here is already the payload from API
console.log(body);
});
})
Verbose - yes!, but does exactly what is needed.

How to handle null response in fetch api

I building a react-native app and using fetch api for handling server request, it is working fine if json returned from the server is not null, but if the response from the server is null it will give me an error-"Json Parse error:Unexpected EOF", below is the code used by me for fetch, I tried to set break-point while debugging to see what is coming in response when null is returned from the server, I am unable to find something on which I can put some check and see if response is null before parsing it, so need help
return fetch(url, //service url{
method: type, // get or post
headers: {
'Accept': 'application/json',
'Content-Type': contentType,
},
body: data //some input parameters
}).then((response) => {
return response.json();
})
.then((responseJson) => {
request.onSuccess(responseJson); // success callback
})
.catch((error) => {
request.onError(error); // error callback
console.error(error);
});

There is a good answer here, but in my case I needed access to the response object after response.text() returns:
function buildResult(response) {
// response.json() crashes on null response bodies
// return {
// data: response.json(),
// identityToken: response.identityToken // sliding expiration...
// };
return new Promise((resolve, reject) => {
response.text().then(body => {
resolve({
data: body.length ? JSON.parse(body) : null,
identityToken: response.identityToken // sliding expiration...
});
}).catch(err => {
reject(err);
});
});
}
//
// the api fetch function
//
function apiFetch(url) {
return fetch(url)
.then(checkStatus)
.then(parseIdentityToken)
.then(buildResult);
}

If the json response null Instead of using response.json() use response.text()
fetch(path)
.then(function (response) {
return response.text()
}).then(function (data) {
resolve(data.length == 0 ? null : JSON.parse(data))
}).catch(err => {
reject(err);
})

If you want to сheck the response request for emptiness:
const response = await fetch(url, options); // your url and options
if (response.ok) {
const contentType = response.headers.get('content-type');
if (contentType && contentType.indexOf('application/json') !== -1) {
const json = await response.json();
successCb(json); // Write your script.
} else {
successCb(); // if the request is successful but the response is empty. Write your script.
}
}