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POST Request using fetch API not returning updated data

I'm trying to make a post request with a string. The server is supposed to return the same string, but with an ID added to it to the response.
However, this is the response (Success: ...) that I am getting:
The server is supposed to return the same string as "sent: ..." with ID added to it, but it's just noting that the POST request was successful.
Here's the code that I am using to accomplish this task (vanilla JS):
function saveForm() {
var street = document.getElementById("street").value;
var provinceId = document.getElementById("province").value;
var provinceName = provinces[provinceId]
var cityId = document.getElementById("city").value;
var cityName = cities[cityId].name
var message = document.getElementById("message").value;
var postData = {
Notes: message,
Address: `${provinceName},${cityName},${street}`,
};
// sent: {...}
console.log("sent: ", JSON.stringify(postData));
fetch("https://wavy-media-proxy.wavyapps.com/investors-notebook/inst1/", {
method: "POST",
body: JSON.stringify(postData),
headers: {
"Content-Type": "application/x-www-form-urlencoded",
},
})
.then((data) => {
console.log("Success: ", data);
})
.catch((error) => {
console.error("Error:", error);
});
}
The server has CORS blocked, and I need to change the content-type to "application/x-www-form-urlencoded" as compared to the usual "application/json"
To solve this issue I tried changing the data format to be an object. I also tried to console.log the data in different formats. I checked the network tab, and have not found anything there in the response.
I am out of options but to ask for help. Any ideas would be greatly appreciated.
EDIT: The admin of the server told me he gave me the wrong format for the POST request. It has to include 'entry'.

You should add then((response) => response.json()) after fetch() function to get the response in JSON format, so it should look like:
fetch("https://wavy-media-proxy.wavyapps.com/investors-notebook/inst1/", {
method: "POST",
body: JSON.stringify(postData),
headers: {
"Content-Type": "application/x-www-form-urlencoded",
},
})
.then((response) => response.json())
.then((data) => {
console.log("Success: ", data);
})
.catch((error) => {
console.error("Error:", error);
});
You can read more about fetch API in the official doc: https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch#uploading_json_data

Maybe your backend API does not return what you expect? When replacing it with another API and changing the content type to application/json it works:
fetch("https://jsonplaceholder.typicode.com/users/", {
method: "POST",
body: JSON.stringify({Post:123,Data:456}),
headers: {
"Content-Type": "application/json",
},
})
.then((response) => response.json())
.then((data) => {
console.log("Success: ", data);
})
.catch((error) => {
console.error("Error:", error);
});

fetchAPI not returning response as then() is getting skipped

I am using fetchAPI to do a post call to my router which will fetch data of logged in user.
Below is the code for the same
submit_button.addEventListener('click',getuser)
function getuser()
{
console.log('clicked')
const username=uname_button.value;
const password=age_button.value;
console.log('username'+username)
console.log('password'+password)
const user = {
email: username,
password: password
};
let options = {
method: 'post',
headers: {
'Content-Type': 'application/json;charset=utf-8'
},
body: JSON.stringify(user)
}
fetch('/users', options)
.then(function(response) {
console.log(response)
})
}
When i execute this in browser, data is getting posted successfully but response is not getting printed , not even promise.
when i added debug points, i could see that control is not going inside then() block?
Can anyone help me with how how to solve this issue?

add a catch block after then to see if any error occurred, as follows:
fetch('/users', options)
.then(function(response) { console.log(response) })
.catch(function(error) { console.log(error) })

Remember that fetch returns a Promise containing the Response object. In order to extract the JSON body content from the response, we use the json() method.
fetch('/users', options)
.then(response => response.json())
.then(data => console.log(data))
.catch((error) => {
console.error('Error:', error);
});

Accessing promise data from Node API inside React fetch call

I'm putting together a React app that consumes data from a Node/Express REST API which is currently on my local machine. I've got a simple res.json returning a Sequelize object, and I'm accessing it through a service I made. Obviously, I'm going to be putting the object in state eventually, but I'm currently having difficulty accessing the values.
const options = {
method: "POST",
headers: {
"Content-Type": "application/x-www-form-urlencoded"
},
body: JSON.stringify({email: "matthewharp#gmail.com", password: "M1nerals"})
};
fetch('http://localhost:3000/users/sign_in', options)
.then(response => console.log(response.json()));
I'm getting the results in the console, but they're stuck in the [[PromiseValue]].
I must be missing some kind of async step, but I'm not sure what.

The json method returns a promise, which you also need to await. So do:
fetch('http://localhost:3000/users/sign_in', options)
.then(response => response.json())
.then(obj => console.log(obj));

You're having this error because response.json() return a promise.
you need to do
fetch('http://localhost:3000/users/sign_in', options)
.then(response => response.json())
.then(res => console.log(res));

You need to return the promise from the fetch call or else you need to act on it in the then for the json promise.
const options = {
method: "POST",
headers: {
"Content-Type": "application/x-www-form-urlencoded"
},
body: JSON.stringify({email: "matthewharp#gmail.com", password: "M1nerals"})
};
return fetch('http://localhost:3000/users/sign_in', options)
.then(response => {
console.log(response.json())
return response.json()
}
);
or...
const options = {
method: "POST",
headers: {
"Content-Type": "application/x-www-form-urlencoded"
},
body: JSON.stringify({email: "matthewharp#gmail.com", password: "M1nerals"})
};
fetch('http://localhost:3000/users/sign_in', options)
.then(response => {
console.log(response.json())
response.json().then( result => {
// whatever you're doing with the data here.
}
);

Take a look at the fetch api:
https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch
You need a separate then chained to take the json data once ready, and it will give you the values.
('http://localhost:3000/users/sign_in', options)
.then(function(response) {
return response.json();
})
.then(function(myJson) {
console.log(JSON.stringify(myJson));
});

catching error body using axios post

I am sending a status code 422 from my backend code with response body which contains the description of the error. I am using axios post as below to post a request:
post: function(url, reqBody) {
const request = axios({
baseURL: config.apiUrl,
url: url,
headers: {
'Content-Type': 'application/json',
'Authorization': sessionStorage.getItem('token')
},
method: 'POST',
data: reqBody,
responseType: 'json'
});
return request
.then((res) => {
return res;
})
.catch((error) => {
console.log(error);
return error;
})
}
The problem is when backend is returning error code 422, the error object I am catching has no information about response body. Is there any way I can retrieve the error text?

I had this same issue and the answer (as per Axios >= 0.13) is to specifically check error.response.data:
axios({
...
}).then((response) => {
....
}).catch((error) => {
if( error.response ){
console.log(error.response.data); // => the response payload
}
});
See here for more details.

The "body" of an AXIOS error response depends from the type of response the request had.
If you would like full details about this issue you can see this blogpost: How to catch the body of an error in AXIOS.
In summary AXIOS will return 3 different body depending from the error:
Wrong request, we have actually done something wrong in our request (missing argument, bad format), that is has not actually been sent. When this happen, we can access the information using error.message.
axios.get('wrongSetup')
.then((response) => {})
.catch((error) => {
console.log(error.message);
})
Bad Network request: This happen when the server we are trying to reach does not respond at all. This can either be due to the server being down, or the URL being wrong.
In this case, we can access the information of the request using error.request.
axios.get('network error')
.then((response) => {})
.catch((error) => {
console.log(error.request );
});
Error status: This is the most common of the request. This can happen with any request that returns with a status that is different than 200. It can be unauthorised, not found, internal error and more. When this error happen, we are able to grasp the information of the request by accessing the parameter specified in the snippets below. For the data (as asked above) we need to access the error.response.data.
axios.get('errorStatus')
.then((response) => {})
.catch((error) => {
console.log(error.response.data);
console.log(error.response.status);
console.log(error.response.headers);
})

For those using await/async and Typescript
try {
const response = await axios.post(url, body)
} catch (error) {
console.log(error.response.data);
}

For react native it just worked for me
api.METHOD('endPonit', body)
.then(response => {
//...
})
.catch (error => {
const errorMessage = JSON.parse(error.request.response)
console.log(errorMessage.message)
})

We can check error.response.data as #JoeTidee said. But in cases response payload is blob type? You can get error response body with the below code.
axios({
...
}).then((response) => {
....
}).catch(async (error) => {
const response = error.response
if(typeof response.data.text === function){
console.log(await response.data.text()); // => the response payload
} else {
console.log(response.data)
}
});

I am returning a string from backend but expecting a json as response type. So I need to return an object instead of string for axios to process it properly.

In my case I wanted to retrieve a response 404 error message (body).
I got body with error.response.data but I couldn't display it because the type was ArrayBuffer.
Solution:
axios.get(url, { responseType: 'arraybuffer' }).then(
response => {...},
error => {
const decoder = new TextDecoder()
console.log(decoder.decode(error.response.data))
}
)
Related posts:
Converting between strings and ArrayBuffers

How to get Readable error response from JavaScript Fetch API?

I am working on Reactjs redux on front-end and Rails API as a back-end.
So now I call API with Fetch API method but the problem is I cannot get readable error message like what I got inside the network tabs
this is my function
export function create_user(user,userInfoParams={}) {
return function (dispatch) {
dispatch(update_user(user));
return 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));
});
}
}
But when errors came I cannot figure out how to get readable response message like I got when I check on my browser network tabs
So this is what I got from the network tabs when I got errors.
My console
This is my rails code
def create
user = User.new(user_params)
if user.save
#UserMailer.account_activation(user).deliver_now
render json: user, status: 201
else
render json: { errors: user.errors }, status: 422
end
end
But I cannot find out how can I get that inside my function

Since the text is hidden inside promise within response object, it needs to be handled like a promise to see it.
fetch(bla)
.then(res => {
if(!res.ok) {
return res.text().then(text => { throw new Error(text) })
}
else {
return res.json();
}
})
.catch(err => {
console.log('caught it!',err);
});

Similar to your answer, but with a bit more explanation... I first check if the response is ok, and then generate the error from the response.text() only for the cases that we have a successful response. Thus, network errors (which are not ok) would still generate their own error without being converted to text. Then those errors are caught in the downstream catch.
Here is my solution - I pulled the core fetch function into a wrapper function:
const fetchJSON = (...args) => {
return fetch(...args)
.then(res => {
if(res.ok) {
return res.json()
}
return res.text().then(text => {throw new Error(text)})
})
}
Then when I use it, I define how to handle my response and errors as needed at that time:
fetchJSON(url, options)
.then((json) => {
// do things with the response, like setting state:
this.setState({ something: json })
})
.catch(error => {
// do things with the error, like logging them:
console.error(error)
})

even though this is a bit old question I'm going to chime in.
In the comments above there was this answer:
const fetchJSON = (...args) => {
return fetch(...args)
.then(res => {
if(res.ok) {
return res.json()
}
return res.text().then(text => {throw new Error(text)})
})
}
Sure, you can use it, but there is one important thing to bare in mind. If you return json from the rest api looking as {error: 'Something went wrong'}, the code return res.text().then(text => {throw new Error(text)}) displayed above will certainly work, but the res.text() actually returns the string. Yeah, you guessed it! Not only will the string contain the value but also the key merged together! This leaves you with nothing but to separate it somehow. Yuck!
Therefore, I propose a different solution.
fetch(`backend.com/login`, {
method: 'POST',
body: JSON.stringify({ email, password })
})
.then(response => {
if (response.ok) return response.json();
return response.json().then(response => {throw new Error(response.error)})
})
.then(response => { ...someAdditional code })
.catch(error => reject(error.message))
So let's break the code, the first then in particular.
.then(response => {
if (response.ok) return response.json();
return response.json().then(response => {throw new Error(response.error)})
})
If the response is okay (i.e. the server returns 2xx response), it returns another promise response.json() which is processed subsequently in the next then block.
Otherwise, I will AGAIN invoke response.json() method, but will also provide it with its own then block of code. There I will throw a new error. In this case, the response in the brackets throw new Error(response.error) is a standard javascript object and therefore I'll take the error from it.
As you can see, there is also the catch block of code at the very end, where you process the newly thrown error. (error.message <-- the error is an object consisting of many fields such as name or message. I am not using name in this particular instance. You are bound to have this knowledge anyway)
Tadaaa! Hope it helps!
I've been looking around this problem and has come across this post so thought that my answer would benefit someone in the future.
Have a lovely day!
Marek

If you came to this question while trying to find the issue because response.json() throws "Unexpected token at position..." and you can't find the issue with the JSON, then you can try this, basically getting the text and then parsing it
fetch(URL)
.then(async (response) => {
if (!response.ok) {
const text = await response.text()
throw new Error(text)
}
// Here first we convert the body to text
const text = await response.text()
// You can add a console.log(text), to see the response
// Return the JSON
return JSON.parse(text)
})
.catch((error) => console.log('Error:', error))
.then((response) => console.log(response))

I think you need to do something like this
export function create_user(user,userInfoParams={}) {
return function (dispatch) {
dispatch(update_user(user));
return 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());
return response.json();
})
.then(function(object){
if (object.errors) {
dispatch(update_errors(response));
throw new Error(object.errors);
} else {
console.log("succeed json re");
dispatch(update_user(json));
}
})
.catch(function(error){
this.setState({ error })
})
}
}

You can access the error message with this way:
return 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)
})
;

The best choice is not to catch the error in the fetch because this will be useless:
Just in your api put a response with not code error
static GetInvoicesAllData = async (req,res) =>
{
try{
let pool = await new Connection().GetConnection()
let invoiceRepository = new InvoiceRepository(pool);
let result = await invoiceRepository.GetInvoicesAllData();
res.json(result.recordset);
}catch(error){
res.send(error);
}
}
Then you just catch the error like this to show the message in front end.
fetch(process.env.REACT_APP_NodeAPI+'/Invoices/AllData')
.then(respuesta=>respuesta.json())
.then((datosRespuesta)=>{
if(datosRespuesta.originalError== undefined)
{
this.setState({datosCargados:true, facturas:datosRespuesta})
}
else{ alert("Error: " + datosRespuesta.originalError.info.message ) }
})
With this you will get what you want.

You variables coming back are not in response.body or response.message.
You need to check for the errors attribute on the response object.
if(response.errors) {
console.error(response.errors)
}
Check here https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch
You should actually be returning an error response code from the server and use the .catch() function of the fetch API

First you need to call json method on your response.
An example:
fetch(`${API_URL}`, {
method: 'post',
headers: {
'Accept': 'application/json',
'Content-Type': 'application/json'
},
body: JSON.stringify(userInfoParams)
})
.then((response) => response.json())
.then((response) => console.log(response))
.catch((err) => {
console.log("error", err)
});
Let me know the console log if it didn't work for you.