express-sesison not saving on routes - node.js

Question

I have a ExpressJS server and I would like to implement in Sessions however it doesn't seem to save the sessions.
The flow is to:
POST to /api/login
GET from /api/viewSession
However, the session['stuff'] returns undefined.
I suspected it might be because i'm trying to GET the session from a different URL. So I added a GET method to /api/login but it returned undefined too.
Could somebody point me in the right direction please? I'm a little lost after a few hours of Googling to no avail.
Here below is my code for index.js and my route api.js.
Also, I'm using
NPM - Version 8.3.1
Node - Version v16.14.0
npm i cors - Version 2.8.5
npm i express-session - Version 1.17.2
npm i express - Version 4.17.3
index.js
const express = require('express')
const formidable = require('express-formidable');
const cors = require('cors');
const session = require('express-session');
const api = require('./routes/api');
const app = express()
const port = 3000;
app.use(express.json());
app.use(formidable());
app.use(
cors({
origin: true,
optionsSuccessStatus: 200,
credentials: true,
})
);
app.options(
'*',
cors({
origin: true,
optionsSuccessStatus: 200,
credentials: true,
})
);
app.use(
session({
saveUninitialized: false,
secret: "anyrandomstring",
cookie: { maxAge: 36000000 }
})
);
//Routes
app.use('/api', api);
//Navigation
app.get('/', function (req, res) {
res.render('index');
res.send("Hi!");
})
//App Start
app.listen(port, () => {
console.log(`App Listening on port ${port}`);
})
api.js
"use strict";
const express = require("express");
let router = express.Router();
router
.route('/dump')
.post(async (req, res) => {
console.log(req.fields);
res.send({status: "ok"})
})
router
.route('/login')
.post(async (req, res) => {
//Saving in Session
req.session['stuff'] = "123456";
res.send("Ok");
})
router
.route('/viewSession')
.get((req, res) => {
console.log(req.session['stuff']);
res.send("ok");
})
module.exports = router;
Also, this is the way I send the POST/GET request
$.ajax({
url: "http://localhost:3000" + '/api/login',
type: "POST",
crossDomain: true,
dataType: "json",
data: {},
success: function (response) {
console.log(response);
}
})

Answer 1

If you're making cross-domain requests with XMLHttpRequest and you want to allow cookies to be set by the server handling the request, you need to set withCredentials : true.
Using jQuery:
$.ajax({
url: "http://localhost:3000" + '/api/login',
type: "POST",
crossDomain: true,
xhrFields: { withCredentials: true },
dataType: "json",
data: {},
success: function (response) {
console.log(response);
}
})