I'm kind of new to JS and can't figure out how to make the following work:
I'd like to run functions (for test reasons console) in the different stages of the fetch API. Like run console when fetch started because of click –> then when fetch received a response (text) -> then when the fetch response has been parsed -> and finally when the parsed response text has replaced the HTML of an existing DOM-element.
var doFetch = (url) => {
fetch(url, {
method: "GET",
headers: new Headers({
'X-Requested-With': 'fetch'
})
}){
console.log("fetch request started because of click on element");
}
.then(response => response.text();
console.log("fetch request has received the response text");
)
.then(response => {
let content = new DOMParser().parseFromString(text, "text/html");
console.log("the received request response text was DOMparsed");
})
.then(response => {
let main = content.querySelector('main').innerHTML;
console.log("the parsed response content replaced current HTML");
}
};
Any tips on how to correct the code would be gladly welcomed!
each then block will execute if previous then block return.
Your first console.log statement should be at the start of the doFetch function. It cannot be written where it is currently written in your code.
You should also chain a catch block at the end to catch any errors that might occur in the promise chain.
As a side note, you should use const or let keywords to declare variables instead of var.
const doFetch = (url) => {
console.log("fetch request started because of click on element");
fetch(url, {
method: "GET",
headers: 'X-Requested-With': 'fetch'
})
.then(response => {
console.log("fetch request has received the response text");
return response.text();
})
.then(response => {
console.log("the received request response text was DOMparsed");
return new DOMParser().parseFromString(text, "text/html");
})
.then(response => {
let main = content.querySelector('main').innerHTML;
console.log("the parsed response content replaced current HTML");
})
.catch(error => console.log(error));
};
In order to do chaining you need to return from each .then block. Aslo your first console.log() post the fetch function had incorrect syntax
var doFetch = (url) => {
fetch(url, {
method: "GET",
headers: 'X-Requested-With': 'fetch'
})
.then(response => {
console.log("fetch request has received the response text");
return response.text();
})
.then(response => {
let content = new DOMParser().parseFromString(text, "text/html");
console.log("the received request response text was DOMparsed");
return content
})
.then(content => {
let main = content.querySelector('main').innerHTML;
console.log("the parsed response content replaced current HTML");
});
console.log("fetch request started because of click on element"); // This will be executed first
};
Related
So I moved over a non-reusable fetch request code snippet to my API:
let response = await fetch(visitURL, {
method: 'POST',
headers: {
'Content-Type': 'application/json',
'Authorization': 'Bearer ' + userJWT
},
body: JSON.stringify(endingVisit)
});
if (response.ok) {
let {visitId, createdAt} = await response.json();
const viewVisitDto = new ViewVisitDto(`${visitId}${createdAt}${visitorId}${doctorId}${oldPatientId}`);
return viewVisitDto;
} else {
throw new Error("deactivated!")
}
I was able to get this far:
axios.post(visitURL, {
headers,
body: JSON.stringify(visit)
}).then((response) => {
console.log(response);
}).catch((error) => {
console.log(error);
})
But does not exactly give me the visitId and createdAt from the response and I cannot use a response.ok nor a response.json(). Essentially I need to pull out that visitId and createdAt that should be coming back in the response.
I also tried just using node-fetch library, but although in VS code it seems to accept it, TypeScript is not happy with it even when I do install #types/node-fetch and even when I create a type definition file for it, my API just doesn't like it.
Guessing what you are after is
// don't know axios, but if it returns a promise await it
const dto = await axios.post(visitURL, {
headers,
body: JSON.stringify(visit)
}).then((response) => {
// parse response
return {resonse.visitId, resonse.createdAt}
}).then(({visitId, createdAt}) => {
// form dto (where are other vals)?
return new ViewVisitDto(`${visitId}${createdAt}${visitorId}${doctorId}${oldPatientId}`);
}).catch((error) => {
console.log(error);
})
However - you don't mention where doctorId and oldPatientId come from... You try providing more info, including output of the console.log's and the surrounding code
I have never used fetch before, and have followed the documentation, however, no results are being returned from my backend. When I submit the form, the url changes, and all appears fine in my console, but no response from my express backend.
The following code is what I have after my form in a script tag. Can someone please advise?
async function getSample(url = `http://localhost:3000/lookup/${url}`, data = {}) {
const response = await fetch(url, {
method: 'GET',
headers: {
'Content-Type': 'application/json'
},
body: JSON.stringify(data)
});
return response.json();
}
document.getElementById('search').addEventListener('submit', function(e) {
event.respondWith(
new Response(myBody, {
headers: {'Content-Type': 'application/json'}
})
);
});
You could try creating a promise and then handling the value returned by the fetch with resolve and reject
async function getSample(url = `http://localhost:3000/lookup/${url}`, data = {}){
return new Promise(function (resolve, reject) {
fetch(url, {
method: 'GET',
headers: {
'Content-Type': 'application/json'
},
body: JSON.stringify(data)
}).then(async response => {
if (response.ok) {
response.json().then(json => resolve(json));
} else {
response.json().then(json => reject(json));
};
}).catch(async error => {
reject(error);
});
});
};
You would then call it like
getSample(...)
.then(results => {
//Code when fetch is successful
}.catch(error => {
//Code when fetch fails
};
I think the problem with it returning nothing is that getSample is an async function, but I imagine you're calling it within a program that isn't async, and so whatever code comes after getSample is using trying to use the value returned from getSample, but nothing's been returned yet, so it's using an empty value. Either that or the return of getSample is happening before the fetch completes. I'm not sure of the exact order that things happen, but a promise should fix your problem
Currently I am trying to convert a working fetch POST request into an Axios POST request. However, I keep getting this Error -> 'Uncaught (in promise) Error: Request failed with status code 400'.
This is my working fetch request code below:
async function postData(url ='', data = { }) {
const response = await fetch(url, {
method: 'POST',
headers: {
'Content-Type': 'application/json' },
body: JSON.stringify(data) });
let txoData = await response.json();
let a = txoData.payload.substring(68,134);
console.log(a);
console.log(txoData)
}
postData('https://merchantapi.taal.com/mapi/tx', { 'rawtx': rawtx })
.then(txoData => { return txoData })
.then(a => { return a })
and this is my NOT working convert to Axios attempt below:
async function postData() {
const response = await axios.post('https://merchantapi.taal.com/mapi/tx', {'rawtx': rawtx});
let txoData = await response.json();
let a = txoData.payload.substring(68,134);
console.log(a);
console.log(txoData)
}
postData()
.then(txoData => { return txoData })
.then(a => { return a })
I would greatly appreciate any help on this issue :)) x
To pass custom headers while using axios supply an object containing the headers as the last argument
I'm trying to return a JSON result to my client using IHttpActionResult.
My .Net code, looks like this:
[AllowAnonymous, HttpPost, Route("")]
public IHttpActionResult Login(LoginRequest login)
{
if (login == null)
return BadRequest("No Data Provided");
var loginResponse = CheckUser(login.Username, login.Password);
if(loginResponse != null)
{
return Ok(new
{
message = "Login Success",
token = JwtManager.GenerateToken(login.Username, loginResponse.Roles),
success = true
});
}
return Ok( new
{
message = "Invalid Username/Password",
success = false
});
}
This doesn't work though, as I never seem to see the JSON on the response after my JavaScript fetch:
const fetchData = ( {method="GET", URL, data={}} ) => {
console.log("Calling FetchData with URL " + URL);
var header = {
'Content-Type': "application/json",
}
// If we have a bearer token, add it to the header.
if(typeof window.sessionStorage.accessToken != 'undefined')
{
header['Authorization'] = 'Bearer ' + window.sessionStorage.accessToken
}
var config = {
method: method,
headers: header
};
// I think this adds the data payload to the body, unless it's a get. Not sure what happens with a get.
if(method !== "GET") {
config = Object.assign({}, config, {body: JSON.stringify(data)});
}
// Use the browser api, fetch, to make the call.
return fetch(URL, config)
.then(response => {
console.log(response.body);
return response;
})
.catch(function (e) {
console.log("An error has occured while calling the API. " + e);
});
}
There is no JSON available in the body.
How do I get aresult back to my client to parse? response.body doesn't have the json object.
The console.log shows:
While the request/response shows:
Using striped's advice: console.log(response.json())
I see the message there. It seems to be in the wrong place. Shouldn't it be in the body?
Fetch works like this
Body methods
Each of the methods to access the response body returns a Promise that
will be resolved when the associated data type is ready.
text() - yields the response text as String
json() - yields the result of JSON.parse(responseText)
blob() - yields a Blob
arrayBuffer() - yields an ArrayBuffer
formData() - yields FormData that can be forwarded to another request
I think you need to
return fetch(URL, config)
.then(response => response.json())
.catch(e => console.log("An error has occured while calling the API. " + e));
doc here: https://github.github.io/fetch/
Your are making a GET request but your controller method is expecting a POST request.
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.