I am triggering a bad request on purpose from my backend. The backend using express is answering properly as expected with:
[...]
.catch((error) => {
res.statusCode = 400;
res.json({
msg: "This is some error",
err: error,
});
});
My question is: Is the 400 always showing up in browser console? I thought I handled the error the right way.
And why do I have to retrieve the data in the frontend with
// 400:
function (data) {
var data = data.responseJSON.msg);
}
instead of (similar to 200:)
// 400:
function (data) {
var data = data.msg);
}
I am just wondering, if I do something wrong.
Thanks for any advice
When fetching data asynchronously, any response other than a 2** response code gets handled by a .catch block. So any other response whether it be 4** or 5** gets caught by the catch block and for that reason if you're using a library like Axios or the likes the response from the backend will be in the error.response or data.response in your case.
I wasn't aware of what you're using to carry out the asynchronous fetching of data i.e. Fetch Api so my answer is a generic response and also is the above code complete?
In my experience any error from whatever weither it be am asynchronous call that generates an error always gets logged to the console, but you can from the front end handle those errors in the catch block
The problem is when the console.log tries to output the error, the string representation is printed, not the object structure, so you do not see the .response property or in your case the .responseJSON
By catching your error with an catch block .catch() or if you using async / await you should, usually, wrap the code inside of an try / catch to catch the error otherwise it will always output this red error in the console
Related
I am using the fetch-API to send a GET request to a Spring Boot backend. The request looks somewhat like this:
const response = await fetch(url);
if (response.status === 200) {
// do something
} else {
response.json().then(response => console.log(response));
}
In case that I send a valid request, i.e. the url passed into fetch() is valid, everything works fine. In case that I pass an invalid url into fetch(), however, two things appear to be happenning:
A serer response message is thrown:
My Spring Boot backend return a ResponseEntity with a custom error message as body. This error message is logged inside the else-block of the above code snippet:
While I do expect the second point to be happenning, I cannot explain the first. I don't understand why this server-response error is logged into my browser console. I do have a few catch-blocks inside my code, something like:
const response = await fetch(url).catch(error => console.log(error));
As far as I know, however, fetch only throws an error if a network connection error occurred or similar. A response code not equal to 200 does not result in fetch throwing an error. So, as I said, I don't know where this error message comes from and I was hoping that somebody does, maybe it is something generic to the fetch API that I just don't know?
I recommend using "try catch" to better capture errors.
If the response is positive and it's a json, use a "then" after the fetch.
try {
const response = await fetch(url).then(res => res.json());
// do something
} catch (e) {
console.error(e);
}
If you're getting a 400 error, check the api documentation to see if you're passing the parameter incorrectly. or if that is not the route
I am working on a project with API. API response is 404 not found. I need to handle this status code without a new page. I want to add an window.confirm("not found"). However, I couldnt do that, because when API says 404 there is no response so I couldn't check the response. How can I do that without using new page? How can I handle that? Here is my response code:
const response = await instance.get(`?q=${q}&appid=${appid}`);
if (!response) {
console.log("ceren");
}
It never prints "ceren". I tried response ==="", response ===null, response.data===null, and so on
The response object is never null. It's an object that, along with many other keys, includes the status. Moreover, if the request fails, it will throw an error (due to the await, though outside of this function it will be a Promise rejection), so you can just catch that:
return instance.get(`?q=${q}&appid=${appid}`).then(/*...*/).catch((error) => console.log('Request failed!'));
Or, if you must use an await:
try {
const response = await instance.get(`?q=${q}&appid=${appid}`);
} catch (error) {
console.log('Request failed!');
}
I have the following .then example chain in my React Native client code, currently without a .catch because I am looking for advice on how to set it up:
await getUserInfo(userId, JSON.stringify(ratingsQueryRatingType), 1)
.then(async userRatingData => {
await findMatchHistory(userId, '', 3)
.then(async matchHistoryData => {
These functions make calls to my NodeJS server. The NodeJS server then sends back the data.
I am trying to find out how I can effectively send back an error from the server to the client, and have the .catch part in the client handle that (e.g. with Alert.alert(error)).
I tried to throw an error on my server as follows but then on my server I get Unhandled promise rejection. It appears that it does not send the error back to client.
// Other code before this part
if (response==='Success') {
return res.status(200).json({'status': 'success'})
} else {
throw 'Match record was not confirmed successfully'
}
Or is it common practice to send response objects from the server (instead of Errors) and then handling those on the client with some kind of if-statement, such as the following?
if (results['status']==='success') {
// Code
} else if (results['status']==='failure') {
// Code
}
I do read about .then chaining with .catch being an attractive option so it feels like this would not be the correct solution..
I think we should send error-codes to the client instead of sending message although you can do it too. you can check the status code based on the error occurred on the backend -> https://developer.mozilla.org/en-US/docs/Web/HTTP/Status
Also, on client side you can use interceptor and create an error-handler service layer and based on the code you will be sending to the client side you can handle that. you can follow these steps to setup one for your app : https://bilot.group/articles/using-react-router-inside-axios-interceptors/
And, On the backend side if there is an error try logging it to log files on your server.
// Other code before this part
if (response==='Success') {
return res.status(200).json({'status': 'success'})
} else {
res.status(based on what happened on server).json({'status': 'failure'})
}
For .then channing instead you should use async/await. for better understanding how to use them and convert chain to asyn/await. This doc contains the step-by-step guide: https://advancedweb.hu/how-to-refactor-a-promise-chain-to-async-functions/
I'm trying to log an error from a subscribe, but the error seems... incomplete?
I've never seen this kind of problem, nor could I find anything on Google. The code is the following:
this._http.post(this.urlPath, email).subscribe(
res => {
// stuff
},
err => {
console.log(err) // <- I need to log this
}
);
It works to an extent. When I open the browser's console, in order to check the error, what I get is this:
The thing is, it seems like there's missing information here. If I open the Network tab, the response for this same request looks like this:
As you can see, the real response has more information. I've tried using {observe: "response"}, but to no avail. I should note that if I try using fetch, the response comes complete, but I'd rather use HttpClient.
What is going on here?
When you receive a http error status code you can't access to the payload returned by the service by the same way that in a success case. Is like an special object.
But you can acccess to it doing some like this, using a pipe in your service and an error handler. This is a minimal example of it:
your.service.ts
...
handleError(error) {
return throwError(error.error);
}
return this.http.get ... the rest of your request.pipe(
catchError(this.handleError)
);
...
And where you consume your service, in err you can acces to full response that your error request contains.
...
, error => {
console.warn(error);
}
Or better than, you can throw the entire object to access to the error (response body) and the rest of params, like status code.
I've managed to load data and to save data. But cannot understand the error handling scheme needed.
When everything goes fine I receive the same object in that was sent but with an extra attribute _saving (false).
When something goes wrong, for instance try to store a string instead of a number, I'll get:
Bad request (error on the console, don't want that)
The response object (might be usefull to show an error)
"Uncaught (in promise)" error
Example:
Code:
this.save()
.then(function(result) {
console.log('ok1', result);
}).catch(function() {
console.log('errorHandler1');
});
OK:
Error:
I've been trying to use catch on promises, following this guidelines:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/catch
but had no luck at all.
This should should work buy just changing p1.then to thisObjectThatIWantToSave.save.then but it didn't.
p1.then(function(value) {
console.log(value); // "Success!"
throw 'oh, no!';
}).catch(function(e) {
console.log(e); // "oh, no!"
}).then(function(){
console.log('after a catch the chain is restored');
}, function () {
console.log('Not fired due to the catch');
});
Again, it still stores the information when the data is correct, the problem I see is that I don't have the tools to decide when was the data correctly stored or not and to avoid triggering errors that can be correctly handled.
I'm using
canjs v3.0.0-pre.11
a restful API provided by feathers
Regarding the error handling ...
Bad request (error on the console, don't want that)
There's no way of preventing the error on the console. This is something chrome does.
The response object (might be usefull to show an error)
You can read the reason for the rejection in can-stache like {{promise.reason}}.
"Uncaught (in promise)" error
I'm not sure why this is being thrown as clearly, your catch is being hit. If you change it to:
this.save()
.then(function(result) {
console.log('ok1', result);
},function() {
console.log('errorHandler1');
});
Do you get the same behavior?