POST request to restify with Fetch API not working - node.js

Question

I'm having some major problems understanding why the Fetch API won't let me send a POST request to my restify server.
I have a basic restify server with a route that receives POST requests on /login.
This route works perfectly as intended if I test with Postman or HTTPRequester, but when I then test it on a browser application with the fetch API, I get the following error (in Chrome):
OPTIONS http://localhost:1337/login 405 (Method Not Allowed)
Fetch API cannot load http://localhost:1337/login. Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:3000' is therefore not allowed access. The response had HTTP status code 405. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.
Two issues
I specifically use the POSt method in my request, so why suddenly OPTIONS?
I've already set Access-Control-Allow-Origin: * on my server.
EDIT: I use restify v5.2.0
My server app:
const restify = require('restify');
const app = restify.createServer({
'name': 'API Token Test',
'version': '1.0.0'
});
app.use(restify.plugins.acceptParser(app.acceptable));
app.use(restify.plugins.bodyParser());
app.use(restify.plugins.jsonp());
app.use((req, res, next) => {
res.header('Access-Control-Allow-Origin', '*');
res.header('Access-Control-Allow-Headers', 'X-Requested-With');
return next();
});
app.post('/login', (req, res) => {
db.execute('SELECT idusers, password FROM users WHERE username = ?', [req.body.username], (selError, rows) => {
if (passwordHash.verify(req.body.password, rows[0].password)) {
crypto.randomBytes(256, (err, buf) => {
if (err) return res.status(500).end();
else {
const token = buf.toString('hex');
db.execute('INSERT INTO accesstokens SET userid = ?, token = ?', [rows[0].idusers, token], (insError) => {
if (insError) return res.status(500).end();
else return res.send({ "AccessToken": token });
});
}
});
} else {
res.status(401).end();
}
});
});
app.listen(1337);
(I've left out mysql stuffs and crypto/password-hash -requires, which are irrelevant to the problem)
And my clientside script:
(() => {
document.addEventListener('DOMContentLoaded', () => {
const form = document.querySelector('.loginForm');
form.onsubmit = () => {
const data = JSON.stringify({
'username': form.username.value,
'password': form.password.value
});
let headers = new Headers();
headers.set('Accept', 'application/json');
headers.set('Content-Type', 'application/json');
headers.set('Content-Length', data.length);
fetch('http://localhost:1337/login', {
'method': 'POST',
'headers': headers,
'mode': 'cors',
'cache': 'default',
'body': data
})
.then((result) => result.json())
.then((data) => {
console.log(data);
localStorage.setItem('token', data);
})
.catch((err) => {
console.log(err);
});
return false;
};
});
})();

Answer 1

Appears all CORS support has been moved to this module since restify v5.x.
Installing restify-cors-middleware and adding the following to my app worked:
const corsMiddleware = require('restify-cors-middleware');
const cors = corsMiddleware({
'origins': ['*']
});
app.pre(cors.preflight);
app.use(cors.actual);