Here's what I have going:
import 'whatwg-fetch';
function fetchVehicle(id) {
return dispatch => {
return dispatch({
type: 'FETCH_VEHICLE',
payload: fetch(`http://swapi.co/api/vehicles/${id}/`)
.then(status)
.then(res => res.json())
.catch(error => {
throw(error);
})
});
};
}
function status(res) {
if (!res.ok) {
return Promise.reject()
}
return res;
}
EDIT: The promise doesn't get rejected, that's what I'm trying to figure out.
I'm using this fetch polyfill in Redux with redux-promise-middleware.
Fetch promises only reject with a TypeError when a network error occurs. Since 4xx and 5xx responses aren't network errors, there's nothing to catch. You'll need to throw an error yourself to use Promise#catch.
A fetch Response conveniently supplies an ok , which tells you whether the request succeeded. Something like this should do the trick:
fetch(url).then((response) => {
if (response.ok) {
return response.json();
}
throw new Error('Something went wrong');
})
.then((responseJson) => {
// Do something with the response
})
.catch((error) => {
console.log(error)
});
The following login with username and password example shows how to:
Check response.ok
reject if not OK, instead of throw an error
Further process any error hints from server, e.g. validation issues
login() {
const url = "https://example.com/api/users/login";
const headers = {
Accept: "application/json",
"Content-Type": "application/json",
};
fetch(url, {
method: "POST",
headers,
body: JSON.stringify({
email: this.username,
password: this.password,
}),
})
.then((response) => {
// 1. check response.ok
if (response.ok) {
return response.json();
}
return Promise.reject(response); // 2. reject instead of throw
})
.then((json) => {
// all good, token is ready
this.store.commit("token", json.access_token);
})
.catch((response) => {
console.log(response.status, response.statusText);
// 3. get error messages, if any
response.json().then((json: any) => {
console.log(json);
})
});
},
Thanks for the help everyone, rejecting the promise in .catch() solved my issue:
export function fetchVehicle(id) {
return dispatch => {
return dispatch({
type: 'FETCH_VEHICLE',
payload: fetch(`http://swapi.co/api/vehicles/${id}/`)
.then(status)
.then(res => res.json())
.catch(error => {
return Promise.reject()
})
});
};
}
function status(res) {
if (!res.ok) {
throw new Error(res.statusText);
}
return res;
}
For me,
fny answers really got it all. since fetch is not throwing error, we need to throw/handle the error ourselves.
Posting my solution with async/await. I think it's more strait forward and readable
Solution 1: Not throwing an error, handle the error ourselves
async _fetch(request) {
const fetchResult = await fetch(request); //Making the req
const result = await fetchResult.json(); // parsing the response
if (fetchResult.ok) {
return result; // return success object
}
const responseError = {
type: 'Error',
message: result.message || 'Something went wrong',
data: result.data || '',
code: result.code || '',
};
const error = new Error();
error.info = responseError;
return (error);
}
Here if we getting an error, we are building an error object, plain JS object and returning it, the con is that we need to handle it outside.
How to use:
const userSaved = await apiCall(data); // calling fetch
if (userSaved instanceof Error) {
debug.log('Failed saving user', userSaved); // handle error
return;
}
debug.log('Success saving user', userSaved); // handle success
Solution 2: Throwing an error, using try/catch
async _fetch(request) {
const fetchResult = await fetch(request);
const result = await fetchResult.json();
if (fetchResult.ok) {
return result;
}
const responseError = {
type: 'Error',
message: result.message || 'Something went wrong',
data: result.data || '',
code: result.code || '',
};
let error = new Error();
error = { ...error, ...responseError };
throw (error);
}
Here we are throwing and error that we created, since Error ctor approve only string, Im creating the plain Error js object, and the use will be:
try {
const userSaved = await apiCall(data); // calling fetch
debug.log('Success saving user', userSaved); // handle success
} catch (e) {
debug.log('Failed saving user', userSaved); // handle error
}
Solution 3: Using customer error
async _fetch(request) {
const fetchResult = await fetch(request);
const result = await fetchResult.json();
if (fetchResult.ok) {
return result;
}
throw new ClassError(result.message, result.data, result.code);
}
And:
class ClassError extends Error {
constructor(message = 'Something went wrong', data = '', code = '') {
super();
this.message = message;
this.data = data;
this.code = code;
}
}
Hope it helped.
2021 TypeScript Answer
What I do is write a fetch wrapper that takes a generic and if the response is ok it will auto .json() and type assert the result, otherwise the wrapper throws the response
export const fetcher = async <T>(input: RequestInfo, init?: RequestInit) => {
const response = await fetch(input, init);
if (!response.ok) {
throw response;
}
return response.json() as Promise<T>;
};
and then I'll catch errors and check if they are an instanceof Response. That way TypeScript knows that error has Response properties such as status statusText body headers etc. and I can apply a custom message for each 4xx 5xx status code.
try {
return await fetcher<LoginResponse>("http://localhost:8080/login", {
method: "POST",
headers: {
Accept: "application/json",
"Content-Type": "application/json",
},
body: JSON.stringify({ email: "user#example.com", password: "passw0rd" }),
});
} catch (error) {
if (error instanceof Response) {
switch (error.status) {
case 401:
throw new Error("Invalid login credentials");
/* ... */
default:
throw new Error(`Unknown server error occured: ${error.statusText}`);
}
}
throw new Error(`Something went wrong: ${error.message || error}`);
}
and if something like a network error occurs it can be caught outside of the instanceof Response check with a more generic message i.e.
throw new Error(`Something went wrong: ${error.message || error}`);
The answer by #fny (the accepted answer) didn't work for me. The throw new Error() wasn't getting picked up by the .catch. My solution was to wrap the fetch with a function that builds a new promise:
function my_fetch(url, args) {
return new Promise((resolve, reject) => {
fetch(url, args)
.then((response) => {
response.text().then((body) => {
if (response.ok) {
resolve(body)
} else {
reject(body)
}
})
})
.catch((error) => { reject(error) })
})
}
Now every error and non-ok return will be picked up by the .catch method:
my_fetch(url, args)
.then((response) => {
// Do something with the response
})
.catch((error) => {
// Do something with the error
})
function handleErrors(response) {
if (!response.ok) {
throw Error(response.statusText);
}
return response;
}
fetch("https://example.com/api/users")
.then(handleErrors)
.then(response => console.log("ok") )
.catch(error => console.log(error) );
I wasn't satisfied with any of the suggested solutions, so I played a bit with Fetch API to find a way to handle both success responses and error responses.
Plan was to get {status: XXX, message: 'a message'} format as a result in both cases.
Note: Success response can contain an empty body. In that case we fallback and use Response.status and Response.statusText to populate resulting response object.
fetch(url)
.then(handleResponse)
.then((responseJson) => {
// Do something with the response
})
.catch((error) => {
console.log(error)
});
export const handleResponse = (res) => {
if (!res.ok) {
return res
.text()
.then(result => JSON.parse(result))
.then(result => Promise.reject({ status: result.status, message: result.message }));
}
return res
.json()
.then(result => Promise.resolve(result))
.catch(() => Promise.resolve({ status: res.status, message: res.statusText }));
};
I just checked the status of the response object:
$promise.then( function successCallback(response) {
console.log(response);
if (response.status === 200) { ... }
});
Hope this helps for me throw Error is not working
function handleErrors(response) {
if (!response.ok) {
return new Promise((resolve, reject) => {
setTimeout(() => {
reject({
status: response.status,
statusText: response.statusText,
});
}, 0);
});
}
return response.json();
}
function clickHandler(event) {
const textInput = input.value;
let output;
fetch(`${URL}${encodeURI(textInput)}`)
.then(handleErrors)
.then((json) => {
output = json.contents.translated;
console.log(output);
outputDiv.innerHTML = "<p>" + output + "</p>";
})
.catch((error) => alert(error.statusText));
}
Another (shorter) version that resonates with most answers:
fetch(url)
.then(response => response.ok ? response.json() : Promise.reject(response))
.then(json => doStuff(json)) //all good
//next line is optional
.catch(response => handleError(response)) //handle error
I have a method that uses node-fetch to make a POST call to update a profile object in a table via an API. If an invalid profileId is provided (status 404) the promise still resolves. What's the best way to handle it so that I can only accept status 200? The method is defined as:
async function updateUserProfileSocketId(profileId, socketId) {
const body = { id: profileId, socketId };
try {
const response = await fetch(`${API_URL}/updateUserProfile`, {
method: 'post',
body: JSON.stringify(body),
headers: { 'Content-Type': 'application/json' },
});
if (response.status !== 200) {
throw new Error(response.status);
}
} catch (err) {
console.log(`updateUserProfileSocketId Error: ${err}`);
}
}
And the method is called in a service class like this:
onInit(socket) {
socket.on('init', (profile) => {
Promise.resolve(updateUserProfileSocketId(profile.id, socket.id))
.then((response) => {
if (response === null || response === undefined) {
console.log(`Unable to find profile ${profile.id}`);
socket.conn.close();
} else {
users.push(profile.id);
}
})
.catch((err) => {
console.log(err);
});
});
}
This seems to work, but I'm not sure if this is the best way to handle this. Any ideas?
If the response status is not 200, you throw an exception that will immediately be caught again. This is probably not what you want. You can leave the catch block for logging purposes, but you should rethrow the exception:
async function updateUserProfileSocketId(profileId, socketId) {
const body = { id: profileId, socketId };
try {
const response = await fetch(...);
if (response.status !== 200) {
throw new Error(response.status);
}
} catch (err) {
console.log(`updateUserProfileSocketId Error: ${err}`);
throw err;
}
}
The same thing applies to the catch-handler inside the socket-callback.
However, removing the try/catch/log/rethrow logic and handling the exception centrally would be cleaner.
Hi I'm new so sorry if my question does not formulate properly.
I want to define a promise from axios js in a global function.
Here I want to handle / catch the 401 status globally and logout the user.
I do not want to handle it in every single query.
Here my source global function to handle a request:
export function requestData (url, payload = {}) {
return axios.post(url, payload)
.then(response => {
return response.data
})
.catch(error => {
if (error.response.status === 401) {
logout()
} else {
return error
}
})
}
And here a example function I use on a controller:
requestData('/api/persons', {options: this.options, search: search})
.then(data => {
this.data = data
})
.catch(error => {
this.error = error.toString()
})
My Problem is that the promise catch in my controller will not fire when there is an exception. How to realize this?
change return error in your requestData function to throw error
As per the Axios docs
You can intercept requests or responses before they are handled by then or catch.
You're going to want to use the Response Interceptor:
axios.interceptors.response.use(function(response) {
// Do something with response data
return response;
}, function(error) {
// Do something with response error
if (error.status === 401) {
logout()
}
return Promise.reject(error);
});
Replacing return error by throw error is the half work.
When I'm right the throw error in promise catch will not invoke the next promise .catch statement. This will work in the .then statement.
This way it should work:
export function requestData (url, payload = {}) {
return axios.post(url, payload)
.then(response => {
return response.data
})
.catch(error => {
if (error.response.status === 401) {
logout()
} else {
return error
}
})
.then(result => {
if (result instanceof Error) {
throw result
} else {
return result
}
})
}
I am trying to wrap Ajax into a Bluebird promise wrapper, but am receiving:
Error: Unhandled rejection (stack trace here...)
wrapper1.js
let fetch = require('./wrapper2');
function requestWeb(type, url, data) {
return new Promise(function(resolve, reject) {
url = config.serverUrl + url.trim();
let options = {
type: type,
data: data ? JSON.stringify(data) : null,
dataType: 'json',
contentType: 'application/json',
crossDomain: true,
timeout: 15000,
xhrFields: { withCredentials: true }
};
fetch(url, options)
.then(data => {
resolve(data);
})
.catch(err => {
console.log('web api error: ' + err.message);
notify('Please check your interet connection');
reject(err);
});
});
}
wrapper2.js
import Promise from 'bluebird';
export default function(url, options) {
return new Promise(function(resolve, reject) {
$.ajax(url, options)
.done((result) => {
resolve(result);
})
.fail((xhr, err) => {
let proxy = new Error();
proxy.message = err || 'error is null';
proxy.name = 'ajax error';
reject(proxy);
});
});
}
Please note Bluebird requires different error object on reject().
I figured it out, BlueBird wants to warn you that a reject() call has been fired but you are not catching it. So I was using...
requestWeb(type, url, data).then((result)=>{});
So to fix, do one of two things: add the .catch() to the end of the call, or remove the reject(err) from the promise.
Here is the code in question:
new Promise((resolve, reject) => {
const opts = {
credentials: 'same-origin',
};
fetch(`/_api/myAPI`, opts)
.then((res) => {
if (!res.ok) {
reject(res);
} else {
...
If the url throws an exception a 401, when the execution reaches reject(res); it throws Uncaught (in promise)
Even after I add a .catch after the .then call, i.e.
fetch(`/_api/myAPI`, opts)
.then((res) => {
if (!res.ok) {
reject(res);
} else {
...
})
.catch((e) => {
console.log(e);
}
it still happens.
Why reject will throw this exception and how can I fix it? My experience is limited to jQuery.Promise and I don't a reject within a failure handler will trigger this error.
When you're rejecting the promise, you're immediately rejecting the promise that is wrapping that entire operation, so you would never get to that catch block.
An analogy: reject and resolve are to promises as return is to functions.
I think what you are trying to do is the code below.
new Promise((resolve, reject) => {
const opts = {
credentials: 'same-origin',
};
fetch(`/_api/myAPI`, opts)
.then((res) => {
if (!res.ok) {
return Promise.reject()
} else {
...
resolve(...);
})
.catch((e) => {
console.log(e);
reject();
}
}