Set cookie after fetch request response from auth server - express

Question

I just started learnign about the express library, im developing an app that access restricted info about a user using an Eve Online API, to do this the user is redirected to an authentication page to get an access and refresh token.
Everything works fine until I try to pull the 'refresh_token' from the response and set a cookie with it.
The error:
(node:20600) UnhandledPromiseRejectionWarning: TypeError: res.cookie is not a function
My code:
const url = 'https://login.eveonline.com/v2/oauth/token';
const options = {
'method':'POST',
headers:
{
'authorization':'Basic '+ process.env.ENV_PASS,
'Content-Type':'application/x-www-form-urlencoded',
'host':'login.eveonline.com'
},
body:''
}
function send_get_request(req, res){
options.body =`grant_type=authorization_code&code=${req.query.code}`
fetch(url,options,{credentials:'include'})
.then(handle_stream)
.then(handle_json)
.then(set_cookie)
.then(redirect_home)
}
function handle_stream(res){
return res.json() //handless data stream, returns responce
}
function handle_json(res){
return res.refresh_token
}
function set_cookie(res){
return res.cookie('refresh_token','hello')
}
function redirect_home(res){
res.redirect('http://localhost:3000/home')
}
router.get('/',send_get_request)
I tried breaking the .then() block but still res.cookie doesn't exits. Also tried using credentials but it doesn't work.

Answer 1

Your code contains two variables res: One stands for the response that your middleware sends back to the client, the other stands for the response you are receiving from the fetch operation. Only the handle_stream function operates on the latter, whereas set_cookie and redirect_home operate on the former.
The last three function are also synchronous and need not be chained with .then. The are invoked synchronously in a function that takes as parameter the json which handle_stream produces asynchronously.
function send_get_request(req, res){
options.body =`grant_type=authorization_code&code=${req.query.code}`;
fetch(url,options,{credentials:'include'})
.then(handle_stream)
.then(function(json) {
var refresh_token = handle_json(json);
set_cookie(res, refresh_token);
redirect_home(res);
});
}
It is all perhaps easier to understand with the async-await syntax:
async function send_get_request(req, res){
options.body =`grant_type=authorization_code&code=${req.query.code}`;
var response = await fetch(url,options,{credentials:'include'});
var json = await handle_stream(response);
var refresh_token = handle_json(json);
set_cookie(res, refresh_token);
redirect_home(res);
}