Solving CORS using a firebase function - node.js

Question

As you know we can't fetch a url on a client side due to CORS.
I am trying to create a function, that will fetch the file for me with the right headers as an agent, and will return it to the client.
So, on Firebase Function :
exports.urlToBlob = functions.https.onRequest((request,response) => {
cors(request, response, () => {
var url = "https://..."; //request.query.url;
fetch (
url,
{
method: 'GET',
headers: { 'Accept': '*/*' }
}
)
.then ((res) => {console.log(res);return res;})
.catch((err) => response.status(400).send(err))
});
});
I can see that it will access the url and get a respond on shell simulator, but not on browser, which will return nothing.
The client suppose to access it with :
var url = "https://us-central1-myproject-6xxxx.cloudfunctions.net/urlToBlob";
$.get(
url,
{url :imgurl, platform : 'xxx'},
function(data) {
console.log(data);
}
);
I know i am doing it wrong, but i have to find a way to use the function to solve the CORS.

Answer 1

Have you tried use cors lib from nodejs.
You can make a configuration for cors to allow cors in your instance.
First install cors lib:
npm install cors --save
After that you can configure cors in you main module application.
As an example:
const cors = require('cors')
//cors config
app.use(cors({
origin: ['https://example.com'] //<-- Here you put the domain you want to call your api
methods: "GET, POST, PUT, DELETE",
optionsSuccessStatus:200,
credentials: true
}))
In your code:
.then ((res) => {console.log(res);return res;})
You should change to:
.then ((res) => {
console.log(res);
//return res;
response.status(200).send(res);
})