CORS block in firebase cloud function - node.js

Question

I'm implementing a cloud function to get results from BigQuery. My functions/index.js code below
const functions = require('firebase-functions');
const {BigQuery} = require('#google-cloud/bigquery');
const cors = require('cors')({origin: true});
exports.getBigQueryData = functions.region('europe-west3').https.onRequest((req,res) => {
cors(req,res,() => {
const bigquery = new BigQuery({
projectId: 'neon-opus-585',
keyFilename: 'service_account_bq.json'
});
const query = "SELECT * FROM `xxxx`";
bigquery.createQueryJob({query: query}).then((data) => {
const job = data[0];
return job.getQueryResults();
})
.then(results => {return res.send(results)})
.catch(error => {console.log(error)})
})
})
When i only deploy / test the function, everything runs OK, but when I use it from inside my application I get the following error
Access to fetch at 'https://xxxx.cloudfunctions.net/xxxx' from origin 'http://localhost:5000' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.
As you can see I tried importing the cors package and implement it in my function as suggesting by several posts here but it is still not working.
Any help would be appreciated :)

Answer 1

Take a look into Handling CORS requests, there you have an example about this:
To handle a preflight request, you must set the appropriate Access-Control-Allow-* headers to match the requests you want to accept:
exports.corsEnabledFunction = (req, res) => {
// Set CORS headers for preflight requests
// Allows GETs from any origin with the Content-Type header
// and caches preflight response for 3600s
res.set('Access-Control-Allow-Origin', '*');
if (req.method === 'OPTIONS') {
// Send response to OPTIONS requests
res.set('Access-Control-Allow-Methods', 'GET');
res.set('Access-Control-Allow-Headers', 'Content-Type');
res.set('Access-Control-Max-Age', '3600');
res.status(204).send('');
} else {
res.send('Hello World!');
}
};
And Authentication with CORS:
If you plan to send a request with an Authorization header, you must:
Add the Authorization header to Access-Control-Allow-Headers.
Set the Access-Control-Allow-Credentials header to true.
Set a specific origin in Access-Control-Allow-Origin (wildcards are not accepted).
exports.corsEnabledFunctionAuth = (req, res) => {
// Set CORS headers for preflight requests
// Allows GETs from origin https://somedomain.com with Authorization header
res.set('Access-Control-Allow-Origin', 'https://somedomain.com');
res.set('Access-Control-Allow-Credentials', 'true');
if (req.method === 'OPTIONS') {
// Send response to OPTIONS requests
res.set('Access-Control-Allow-Methods', 'GET');
res.set('Access-Control-Allow-Headers', 'Authorization');
res.set('Access-Control-Max-Age', '3600');
res.status(204).send('');
} else {
res.send('Hello World!');
}
};