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Angular 10 subscribe is failing to post with error code OK(and no other errors shown)

I am new to angular 10 and I am trying to make an http post to a PHP file as shown below
this.http.post(`${environment.server}/path/file.php`, {param1, param2})
.subscribe(
data => {
console.log(JSON.stringify(data));
},
error => {
console.log(error);
this.error = error;
});
The file is successfully called and returns the following JSON as displayed in the console response
{"Email":null,"school_year":2021,"academic_year":"2021"}
When I make the request I am immediately taken to the error state and all the console log is showing below only prints "OK"
console.log(error);
The two questions are the following
Why am getting to the error when the file is successfully returning JSON
Is there a way to get a more helpful error message than just OK

You will need to set the content type to application/json
You would be better off if you used a rest API rather than using php files. .NET Core or Node.JS would give you a better development experience.

It seems that your back-end PHP send the response with status code 400. It should be revised to 200 to get the data in response. When Status code is in Error range like 400, 401, 403 ... http Response will resolved in error or catch part.
In addition if you want just get data, it's better to use GET instead of POST.

Process multiple unique Express JS requests

I've got a small Express JS api that I'm building to handle and process multiple incoming requests from the browser and am having some trouble figuring out the best approach to handle them.
The use case is that there's a form, with potentially up-to 30 or so people submitting form data to the Express JS api at any given time, the API then POSTS this data of to some place using axios, and each one needs to return a response back to the browser of the person that submitted the data, my endpoint so far is:
app.post('/api/process', (req, res) => {
if (!req.body) {
res.status(400).send({ code: 400, success: false, message: "No data was submitted" })
return
}
const application = req.body.Application
axios.post('https://example.com/api/endpoint', application)
.then(response => {
res.status(200).send({ code: 200, success: true, message: response })
})
.catch(error => {
res.status(200).send({ code: 200, success: false, message: error })
});
})
If John and James submit form data from different browsers to my Express JS api, which is forwarded to another api, I need the respective responses to go back to the respective browsers...

Let's make clear for you, A response of a request will only send to the requester, But if you need to send a process request and send a response like, hey i received your request and you can use another get route to get the result sometimes later, then you need to determine which job you mean. So You can generate a UUID when server receives a process request and send it back to the sender as response, Hey i received your process request, you can check the result of process sometimes later and this UUID is your reference code. Then you need to pass the UUID code as GETparam or query param and server send you the correct result.
This is the usual way when you are usinf WebSockettoo. send a process req to server and server sends back a reference UUID code, sometime later server sends the process result to websocket of requester and says Hey this is the result of that process with that UUID reference code.
I hope i said clear enough.

Uncaught (in promise) SyntaxError: Unexpected end of JSON input

I am trying to send a new push subscription to my server but am encountering an error "Uncaught (in promise) SyntaxError: Unexpected end of JSON input" and the console says it's in my index page at line 1, which obviously is not the case.
The function where I suspect the problem occurring (because error is not thrown when I comment it out) is sendSubscriptionToBackEnd(subscription) which is called in the following:
function updateSubscriptionOnServer(subscription) {
const subscriptionJson = document.querySelector('.js-subscription-json');
const subscriptionDetails = document.querySelector('.js-subscription-details');
if (subscription) {
subscriptionJson.textContent = JSON.stringify(subscription);
sendSubscriptionToBackEnd(subscription);
subscriptionDetails.classList.remove('is-invisible');
} else {
subscriptionDetails.classList.add('is-invisible');
}
}
The function itself (which precedes the above function):
function sendSubscriptionToBackEnd(subscription) {
return fetch('/path/to/app/savesub.php', {
method: 'POST',
headers: {
'Content-Type': 'application/json'
},
body: JSON.stringify(subscription)
})
.then(function(response) {
if (!response.ok) {
throw new Error('Bad status code from server.');
}
return response.json();
})
.then(function(responseData) {
if (!(responseData.data && responseData.data.success)) {
throw new Error('Bad response from server.');
}
});
}
I have tried replacing single quotes with double quotes in the fetch call but that yields the same results.
I know that the JSON should be populated because it prints to the screen in the updateSubscriptionOnServer() function with subscriptionJson.textContent = JSON.stringify(subscription);, and I used that output in the google codelab's example server to receive a push successfully.
EDIT: Here is the JSON as a string, but I don't see a mistake in syntax:
{"endpoint":"https://fcm.googleapis.com/fcm/send/dLmthm1wZuc:APA91bGULRezL7SzZKywF2wiS50hXNaLqjJxJ869y8wiWLA3Y_1pHqTI458VIhJZkyOsRMO2xBS77erpmKUp-Tg0sMkYHkuUJCI8wEid1jMESeO2ExjNhNC9OS1DQT2j05BaRgckFbCN","keys":{"p256dh":"BBz2c7S5uiKR-SE2fYJrjPaxuAiFiLogxsJbl8S1A_fQrOEH4_LQjp8qocIxOFEicpcf4PHZksAtA8zKJG9pMzs=","auth":"VOHh5P-1ZTupRXTMs4VhlQ=="}}
Any ideas??

This might be a problem with the endpoint not passing the appropriate parameters in the response's header.
In Chrome's console, inside the Network tab, check the headers sent by the endpoint and it should contain this:
Example of proper response to allow requests from localhost and cross domains requests
Ask the API developer to include this in the headers:
"Access-Control-Allow-Origin" : "*",
"Access-Control-Allow-Credentials" : true

This happened to me also when I was running a server with Express.js and using Brave browser. In my case it was the CORs problem. I did the following and it solved the problem in my case:
(since this is an Express framework, I am using app.get)
-on the server side:
res.set({
"Content-Type": "application/json",
"Access-Control-Allow-Origin": "*",
});
-on client side I used Fetch to get data but disabled the CORS option
// mode: "no-cors" //disabled this in Fetch
That took care of my issues with fetching data with Express

This can be because you're not sending any JSON from the server
OR
This can be because you're sending invalid JSON.
Your code might look like
res.end();

One of the pitfalls is that returned data that is not a JSON but just a plain text payload regardless of headers set. I.e. sending out in Express via something like
res.send({a: "b"});
rather than
res.json({a: "b"});
would return this confusing error. Not easy to detect in network activity as it looks quite legit.

For someone looking here later. I received this error not because of my headers but because I was not recursively appending the response body to a string to JSON.parse later.
As per the MDN example (I've taken out some parts of their example not immediately relevant):
reader.read().then(function processText({ done, value }) {
if (done) {
console.log("Stream complete");
return;
}
result += chunk;
return reader.read().then(processText);
});
For my issue I had to
Use a named function (not an anonymous ()=>{}) inside the .then
Append the result together recursively.
Once done is true execute something else on the total appended result
Just in case this is helpful for you in the future and your issue is not header related, but related to the done value not being true with the initial JSON stream response.

I know this question has already been answered but just thought I add my thoughts.
This will happen when your response body is empty and response.json() is expecting a JSON string. Make sure that your API is returning a response body in JSON format if must be.

RESTful Get Request with Angular & NodeJS Express

I'm just following tutorials and figuring out how to handle get requests in NodeJS.
Here are snippets of my code:
NodeJS:
router.get('/test', function(request, response, next) {
console.log("Received Get Request");
response.jsonp({
data: 'test'
});
});
Angular:
$http.get("http://localhost:3000/test").
success(function(response) {
alert("OK");
}).
error(function(response) {
alert("FAIL");
});
If I try to access the link directly # localhost:3000/test, I'm able to receive the JSON message correctly. But when I use angularJS $http call, the request always fails and I'll find this error in the network inspector (Response)
SyntaxError:JSON.parse:unexpected end of data at line 1 column 1 of
the JSON data
The reason for that is because the response is empty but the response code is 200 in both cases.
I've tried searching for hours but maybe someone can enlighten me on this?

you could try and send
res.send('test')
and then on your http request you can use 'then'
$http.get("http://localhost:3000/test").then(function(res) {
console.log(res);
})
unlike success, then will give you a complete object (with 'test' - string as res.data)
success will bring you only the data;
then will bring you the whole object (with the status and such)..
now about that jsonp .. it's used to override a json response. you could simply use 'res.json({data: 'test'})' and it should also work for you..
hope it helps

You're using jsonp in node, which you probably don't need to. This adds extra characters to the response and so the JSON parser fails to parse (that's what the error is telling you, the JSON is malformed)
Try changing the server to look like
response.json({
data: 'test'
});
If you look in the Network pane of the developer tools, you should be able to see the raw response. It should look something like:
{"data" : "test"}

Error handling in Express JS after response

I have been trying different error handling techniques with Express. First I was just using process.on('uncaughtException'). I quickly learned that it was bad practice. After that, I tried using the new "Domain" feature in node js. I wrapped each request in a domain, however, if I would send a response and then do some more work on the server (dealing with the same request) it would not catch the errors from those functions after the response was sent. I then tried moving to the built-in error handling with Express using next(err). However, I am running into the same situation. If I send a response and then a function has an error after the response has been sent, my error handler is not called. Here is some code as an example.
async.waterfall([
function(after)
{
hashPassword(password, after);
},
function(hash, after)
{
makeToken(hash, after);
},
function(hash, token, after)
{
insertUserInfo(email, username, hash, ip, token, after);
},
function(token, id, after)
{
req.session.attempts = 0;
res.json({ err: 0, attempts: 0 }); //Response is sent
after(null, token, id);
},
function(token, id, after)
{
sendEmail(token, email, renderEmail); //Errors not caught
makeFolder(id, after); //Errors not caught
}
], function(err) {
if(err)
next(err);
}
);
As you can see from the code, I am registering a new user. Now, I could wait until I have completed all of my logic to send back the response but I thought that it would make the request appear much faster for the user if I did some of the less important things after the response has been sent. I am willing to change my code to perform everything THEN send the response, but I want to make sure that there is no solution out there that I have not tried yet.

As awesome as Express JS is, it doesn't have a time travel feature allowing you to unsend a request :) This is really the root of your problem. If your response must display the outcome, then it must wait until all the relevant actions to complete.