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Will the 'error' event ever be emitted on 'http.IncomingMessage' in a node.js http.request?

I can create 4 error scenarios when calling http.get(url, cb):
httpThrows()
Can be triggered with a wrong format of the url, or wrong callback, etc.
function httpThrows() {
try {
http.get("www.missing-protocol.com", res => {
console.log(res.statusCode);
});
} catch (error) {
console.log("http.get() throws an error.");
}
}
requestError()
It the main error handler and triggers on some network related issue, e.g. DNS lookup failed or server not responding, etc.
function requestError() {
var req = http.get("http://some-url-that-does-not-exist.com", res => {
console.log(res.statusCode);
});
req.on("error", err => {
console.log("req.on('error') called with error");
});
}
errorCode()
Server responded normally so no network errors (can handle server errors).
function errorCode() {
http.get("http://httpstat.us/501", res => {
console.log("Got error code:", res.statusCode);
});
}
responseError() (the problem)
An http.IncomingMessage is given in the callback as response or res. According to the documentation it is a Readable steam and that steam can emit an error event.
function responseError() {
http.get("http://some-ulr-with-error-halfway-through.com/", res => {
console.log(res.statusCode);
// This will never be emitted?
res.on("error", err => {
console.log("res.on('error') called with error", err);
});
});
}
So this last handler:
Is this event ever triggered when using http.request or http.get?
If so what can trigger the event?

For my understanding the only way to end up with an error in that case is if there would be an issue with Node or the Engine and in both cases you can't do much about it.
In this situations I prefer not to handle those cases because you have less code to review and maintain.

JS-Data addAction method throws instead of rejecting the promise with the error message

In the js-data library, I have added a custom query with the addAction() method as shown here. Now when my server returns a 4xx error code upon calling that custom action, an error is thrown but the server response (which is send) is nowhere to be found:
store.getMapper('school').getTeacherReports(1234, {
basePath: 'reports'
}).then(function(response) {
console.log('response', response.data)
}).catch(function(err) {
console.log('err', err);
})
How should I handle this? Is there some method I don't know of that I should use? I already tried the response and responseError properties in the addAction() according to the docs.

The then function can take two parameters:
then(
onSuccess: Function,
onRejection: Function
)
So here is how you can handle the rejection due to the 4xx error:
store.getMapper('school').getTeacherReports(1234, {
basePath: 'reports'
}).then(
function (response) { // on success
console.log('response', response.data);
},
function (error) { // on error
console.error(error);
},
)

This has to do with axios: The rejected error object indeed has the response as a property (source code) but it doesn't appear as such in console outputs because error objects are shown differently in the console.
The following shows the underlying properties:
store.getMapper('school').getTeacherReports(1234, {
basePath: 'reports'
}).then(function(response) {
console.log('response', response.data)
}).catch(function(err) {
let errorObject = JSON.parse(JSON.stringify(error))
console.log(errorObject)
});

Proper mindset for use of promises?

I've only recently looked at promises (JS not being my forte) and I'm not sure what the proper way to do this is. Promises are supposed to prevent right-drifting code but when I end up with somewhat complex logic I end up nested far too deep anyway, so I'm convinced I'm doing it wrong.
If I'm returning both successes and failures as json values, and I want to handle malformed json as well, I immediately think to do something like this:
fetch('json').then(function (result) {
return result.json();
}).catch(function (result) {
console.error("Json parse failed!");
console.error(result.text);
}).then(function (wat) {
// if (!result.ok) { throw...
}).catch(function (wat) {
// Catch http error codes and log the json.errormessage
});
Of course, this won't work. This is stereotypical synchronous code. But it's the first thing that comes to mind. Problems I can see:
How do I get both the response and the json output?
How do I get separate control flow for errors and successes?
How do I catch a json parse error on both types of response?
My best attempt involves nesting to the point where I might as well be using callbacks, and it doesn't work in the end because I still haven't solved any of the above problems:
fetch('json').then(function (response) {
if (!response.ok) {
throw response;
}
}).then(
function (response) {
response.json().then(function (data) {
console.log(data);
});
},
function (response) {
response.json().then(function (data) {
console.error(data.errormessage);
});
}
).catch(function () {
console.error("Json parse failed!");
// Where's my response????
});
What's the "Right" way to do this? (Or at least less wrong)

If you want to call response.json() anyway (for successful and failed response) and want to use the response together will the response data. Use Promise.all:
fetch('json')
.then(response => Promise.all([response, response.json()]))
.then(([response, data]) => {
if (!response.ok) {
console.error(data.errormessage);
} else {
console.log(data);
}
})
.catch(err => {
if (/* if http error */) {
console.error('Http error');
} else if (/* if json parse error */)
console.error('Json parse failed');
} else {
console.error('Unknown error: ' + err);
}
});

You shouldn't use exceptions for control flow in Promises any more than you should when not using Promises. That's why fetch itself doesn't just reject the promise for status codes other than 200.
Here's one suggestion, but the answer will necessarily depend on your specific needs.
fetch('json').then(function (response) {
if (!response.ok) {
response.json().then(function (data) {
console.error(data.errorMessage);
});
return ...;
}
return response.json().catch(function () {
console.error("Json parse failed!");
return ...;
});
}).catch(function (e) {
console.error(e);
return ...;
});

Parse CloudCode sometimes does not work

I want to update a field in the 'NotesDB' that indicates the number of comments on a specific Note. Parse Cloudcode should do this automatically after saving a comment.
In practice it sometimes does and it sometimes doesn't (even with the same user, on the same note). The comment itself is always saved properly.
Is there any way i can improve this code..?
Parse.Cloud.afterSave("CommentsDB", function(request) {
var OriginalNote = request.object.get("OriginalPostId");
var query = new Parse.Query("NoteDB");
query.get(OriginalNote, {
success: function(post) {
post.increment("NumberOfComments");
post.save();
},
error: function(error) {
console.log("An error occured :(");
}
});

As you code stands, it is not possible to see if the post.save() call is failing or not (and if it is, why), maybe try chaining your promises :
query.get(OriginalNote,{useMasterKey:true}).then (function (post) {
post.increment("NumberOfComments");
return post.save(null,{useMasterKey:true});
}).then (function (savedPost) {
console.log('post incremented ok to ' + savedPost.get('NumberOfComments'));
},function (err) {
//this function will catch any error in the promise chain : query.get() or post.save()
console.error('An error occured : ' + err.message);
});

Javascript http get success function capturing error response

I am making a http request to a url which is returing a 500 error response(This is the expected behavior). But this is error is getting captured in the success function instead of error function.
$http.get("myUrl")
.then(function (response) {
console.log(response);
}
.function (error) {
// Handle error here
});
Please help in understanding this and the correct way to use this.

It should be either:
$http.get("myUrl")
.then(function (response) {
console.log(response);
}
,function (error) {
// Handle error here
});
Or
$http.get("myUrl")
.then(function (response) {
console.log(response);
})
.catch (function(error) {
// Handle error here
});

If this is angulars $http, it's supposed to be something like this:
$http.get("myUrl")
.then(
function (response) {
console.log(response);
},
function (error) {
// Handle error here
}
);
You want two functions as your arguments to then(). The first is your successCallback, the second your errorCallback.
As an alternative you may add an catch() to your promise chain. Which is easier to read and prevents errors like yours.

I had an interceptor in my application which was causing the problem.
All my error responses were intercepted and returned without a status. Below is the code.
return {
'responseError': function(config) {
if(config.status===401){
//Do Something
return config;
}
return config;
}
}
Changing the return statement to return $q.reject(config); started returning the correct status.