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Passing JSON array to cloud function node js

I am trying to convert a javascript object array to JSON to pass it with the POST request to the cloud function. However when I use the JSON.parse() function I get an error:SyntaxError: Unexpected token u in JSON at position 0
Can someone tell me what I'm doing wrong, this is my POST request:
const body = `{
"item":[
{"firstName":"John", "lastName":"Doe"},
{"firstName":"Anna", "lastName":"Smith"},
{"firstName":"Peter", "lastName":"Jones"}]
}`;
const init = {
method: 'POST',
body
};
fetch('https://us-central1-web-app-bbo-prod.cloudfunctions.net/TestObject', init)
.then((response) => {
return response.json(); // or .text() or .blob() ...
})
.then((text) => {
// text is the response body
})
.catch((e) => {
// error in e.message
});
and this my cloud function:
exports.TestObject = functions.https.onRequest(async(request, response)=> {
var corsFn = cors();
corsFn(request, response, async function() {
const myJSON = request.body.item;
console.log(JSON.parse(myJSON))
//console.log(item)
})})

TLDR:
Server: remove JSON.parse
Client: change init to
const init = {
method:'POST',
body:JSON.stringify(body),
headers: {
'Content-Type':'application/json'
}
}
Explained:
You've got three issues I see.
Anytime you see the following you are calling JSON.parse on invalid stringified JSON.
SyntaxError: Unexpected token u in JSON at position 0
First, req.body should already be JSON if everything's working properly and you received JSON. To call JSON.parse(req.body.item) is to pass an Object to a function that takes strings. You can just refer to req.body.item.
Second you have to make sure you're sending the correct body, you are passing an object as the body for the fetch function. I'm not familiar with the fetch function but a quick look at the Mozilla examples indicate that should it should be stringified, i.e. body:JSON.stringify(body). The object you pass likely is either converted to form data or has toString() called on it and you're sending [object Object].
// REPL
> ({foo:'bar'}).toString()
'[object Object]'
Third, you have to make sure it gets parsed properly on the backend.
According to the GCloud nodeJS docs the nodejs google cloud functions implement an endpoint for an Express Router.
Normally if you wanted to use JSON the way you are you would need the body parser BodyParser middleware. The examples here (GCloud HTTP Functions) indicate that the body-parser middleware is already instead and working based off of Content-Type header.
Since it's deciding whether to parse it as JSON based on content type you want to set the header in your fetch function as 'content-type':'application/json'.

Error: SyntaxError: Unexpected end of JSON input at fetch.then.response

I get this error every time I try to use the POST method in my API.
SyntaxError: Unexpected end of JSON input at fetch.then.response
When I use the GET method I get the data normally.
This is the code:
const teste = () => {
fetch("myURL/test", {
method: "POST",
headers: {
"Content-Type": "application/json"
},
body: JSON.stringify({
id: 1,
name: "Teste",
amount: 1,
value: 3
})
})
.then(response => response.json()) //Here is the error
.then(data => {
console.log(data);
})
.catch((err)=>console.log(err))}
Can someone help me? Thank you.
EDIT:
I just add this line to see the log:
.then(response => console.log(response))
Here is what I got:
Response {
type: "cors",
url: "myURL/test",
redirected: false,
status: 201,
ok: true,
…}
body: (...)
bodyUsed: false
headers: Headers {}
ok: true
redirected: false
status: 201
statusText: ""
type: "cors"
: "myURL/test"
__proto__: Response

It means that the page fetched at myURL/test does not responds with JSON content, or with malformed JSON content. This is not an error in your script, which is fine, this is an error with your server, that is not serving JSON content at myURL/test.
Also, note that servers might not respond similarly to GET requests and POST request for the same URL! If you fetch valid JSON from a GET request but, as you described, failed to fetch valid JSON from a POST request, your server might be serving different content depending on the request type. Investigate that.
Debug tips
Replace then(resp => resp.json()) by then(resp => resp.text()).then(console.log) to see what the served content looks like
Use Postman to simulate API calls, and see what the served content looks like, with more details
Examine the response with the developer tools:
In Chrome
Open the console (F12)
Go to the network tab
Click on the file server by myURL/test
Click on response: that will be the text content. It shoud be properly formatted JSON.

Basically GET method does not send your body object to the server in which you get the response. Only the POST action will send your body object to the server.
I assume that the object you wish to send is the problem. Either the server which you are trying to connect does not expects the body object as string or you should make sure you have parsed the JSON properly before processing.

Looks like the API you're calling, doesn't have a response body on this particular POST. Then when you call response.json() (converting response.body to json) it runs into error.
Or maybe the response is body is not a valid json body.
If you wanna handle this error more fashion way you could go like this:
tryGetJson = async (resp) => {
return new Promise((resolve) => {
if (resp) {
resp.json().then(json => resolve(json)).catch(() => resolve(null))
} else {
resolve(null)
}
})
}
https://github.com/github/fetch/issues/268#issuecomment-399497478

(for people coming later but dealing with this problem)
The problem is most probably server error or invalid URL but you can't see it because all examples on internet how to work with fetch are missing one important part - the server or network failure.
I think the correct way how to deal with fetch is test response if contains errors before conversion to json.
Check the part of the first then in example where it.ok is tested:
async function fetchData() {
return await fetch('https://your-server.com/some-NOt-existing-url/')
.then(it => {
if (!it.ok) {
throw `Server error: [${it.status}] [${it.statusText}] [${it.url}]`;
}
return it.json();
})
.then(receivedJson => {
// your code with json here...
})
.catch(err => {
console.debug("Error in fetch", err);
setErrors(err)
});
}
(note: it is just name convention borrowed from Kotlin, it makes JavaScript code shorter. It is alias for anything on left side of expression so in this case for response)

Node Res.write send multiple objects:

I am trying to send multiple objects in the response as json back to client from one route. It is some kind of middleware, that gets called, and then it calls itself another route inside to get the data and do some data processing. Here is the code:
const axios = require('axios');
var datetime = require('node-datetime');
function MiddlewareRoutes(router) {
var MiddlewareController = require('../controllers/MiddlewareController')
router.route('/Middleware/someotherLink/parametres').get(function(req,res,next) {
console.log(req.params.id, req.params.startTime, req.params.endTime);
url = `http://localhost:hidden/link/..`;
url2 = "http://localhost:port+params..."
axios.get(url) //, {responseType: 'json',}
.then(response => {
var formattedData = formatData(response.data);
[max,min] = getMinMax(formattedData);
res.write("max:",max);
res.write("min:",min);
res.write(formattedData);
res.end();
})
.catch(error => {
console.log(error);
});
})
}
However, I am getting the error:
TypeError: First argument must be a string or Buffer
at write_ (_http_outgoing.js:642:11)
at ServerResponse.write (_http_outgoing.js:617:10)
at axios.get.then.response (C:\Users\U500405\Desktop\Backend\routes\MiddleWare.js:19:13)
at <anonymous>
at process._tickCallback (internal/process/next_tick.js:188:7)
What am I doing wrong? I cannot just send strings, because I have to send objects...

Write is for writing strings to the response body, the parameters accepted are (chunk[, encoding][,callback]), however an object is not a string, and your min/max values are not encodings.
As said before, you could use JSON.stringify to convert an object into a JSON string, however since this is pretty common behaviour Express provides a send method that can do exactly that.
res.write(JSON.stringify({
min,
max,
formattedData
}));
or
res.send({
min,
max,
formattedData
});

res.write(formattedData); Here formatted data is a object . As the error message says, write expects a string or Buffer object, so you must convert it. by doing so : res.write(JSON.stringify(formattedData)) . The node expects the content to not to be a object because it needs string to pass on to the server. The server only understands plain text input as mentioned in Nodejs Docs Nodejs Doc Link for res.write() , and by default the encoding is 'utf-8' . so When sending a object through the server , the server discards it and throws an error of expected buffer chunks or string data.

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.

Cannot extract key/value from json

A resource is fetched in node.js like this:
requestify.post('myurl')
.then(function (response) {
console.log(response);
console.log(response.body);
});
console.log(response) gives:
Response {
code: 200,
body: '{"guid":"abcd","nounce":"efgh"}'
}
console.log(response.body) gives:
{"guid":"abcd","nounce":"efgh"}
However, for some reason I cannot access the key "guid" or "nounce". In both cases I get an undefined.
I have tried both with
console.log(response.body.guid);
and
console.log(response.body['guid']);

The body is string, but you want it to be an object. Just transform it:
JSON.parse(response.body).guid

It seems that the value of body property is a string. You must parse it as JSON:
console.log(JSON.parse(response.body).guid);

You need to set the return type to
response.writeHead(200, {"Content-Type": "application/json"});
so your receiving end will make it an object automagically when received.
See Responding with a JSON object in NodeJS (converting object/array to JSON string)