subzey/index.html

## index.html
<!doctype html>
<html>
    <head><title>Login status demo</title></head>
    <body>
        <fieldset>
            <legend>Псевдо-логинка</legend>
            <form id="loginform">
                <p><label><input name="user" type="input"> Логин</label></p>
                <p><label><input name="password" type="password"> Пароль</label></p>
                <p><input type="submit"></p>
            </form>
        </fieldset>
        <script>
            document.querySelector('#loginform').addEventListener(
                'submit',
                async (e) => {
                    e.preventDefault();
                    const res = await fetch('/api/login', { method: 'POST', body: new FormData(e.target) });
                    const { error } = await res.json();
                    if (!res.ok || error) {
                        alert('Неправильный логин или пароль!');
                    } else {
                        alert('Залогинились!');
                    }
                },
                false
            );
        </script>
    </body>
</html>

## index.mjs
#!/usr/bin/env node

import { createServer } from 'http';
import { createReadStream } from 'fs';
import { resolve } from 'path';
import { URL, fileURLToPath } from 'url';

function apiResponse(req, res) {
    res.writeHead(200, { 'content-type': 'application/json;charset=utf-8' });
    res.end(JSON.stringify({
        error: 'Wrong credentials',
    }));
}

function serveIndex(req, res) {
    const indexPath = resolve(fileURLToPath(import.meta.url), '../index.html');
    console.log(indexPath);
    res.writeHead(200, { 'content-type': 'text/html;charset=utf-8' });
    createReadStream(indexPath).pipe(res);
}

const srv = createServer((req, res) => {
    const { pathname } = new URL(req.url, 'http://localhost/');
    switch (pathname) {
        case '/':
            return serveIndex(req, res);
        case '/api/login':
            if (req.method !== 'POST') {
                res.writeHead(405, { allow: 'POST' });
                res.end();
                return;
            }
            return apiResponse(req, res);
        default:
            res.writeHead(404);
            res.end();
    }
});
srv.on('listening', () => { console.log(`http://127.0.0.1:${srv.address().port}/`); })
srv.listen();

## package.json
{
    "type": "module",
    "name": "auth-api-demo",
    "version": "0.1.0",
    "bin": "./index.mjs"
}
	<!doctype html>
	<html>
	<head><title>Login status demo</title></head>
	<body>
	<fieldset>
	<legend>Псевдо-логинка</legend>
	<form id="loginform">
	<p><label><input name="user" type="input"> Логин</label></p>
	<p><label><input name="password" type="password"> Пароль</label></p>
	<p><input type="submit"></p>
	</form>
	</fieldset>
	<script>
	document.querySelector('#loginform').addEventListener(
	'submit',
	async (e) => {
	e.preventDefault();
	const res = await fetch('/api/login', { method: 'POST', body: new FormData(e.target) });
	const { error } = await res.json();
	if (!res.ok \|\| error) {
	alert('Неправильный логин или пароль!');
	} else {
	alert('Залогинились!');
	}
	},
	false
	);
	</script>
	</body>
	</html>
	#!/usr/bin/env node

	import { createServer } from 'http';
	import { createReadStream } from 'fs';
	import { resolve } from 'path';
	import { URL, fileURLToPath } from 'url';

	function apiResponse(req, res) {
	res.writeHead(200, { 'content-type': 'application/json;charset=utf-8' });
	res.end(JSON.stringify({
	error: 'Wrong credentials',
	}));
	}

	function serveIndex(req, res) {
	const indexPath = resolve(fileURLToPath(import.meta.url), '../index.html');
	console.log(indexPath);
	res.writeHead(200, { 'content-type': 'text/html;charset=utf-8' });
	createReadStream(indexPath).pipe(res);
	}

	const srv = createServer((req, res) => {
	const { pathname } = new URL(req.url, 'http://localhost/');
	switch (pathname) {
	case '/':
	return serveIndex(req, res);
	case '/api/login':
	if (req.method !== 'POST') {
	res.writeHead(405, { allow: 'POST' });
	res.end();
	return;
	}
	return apiResponse(req, res);
	default:
	res.writeHead(404);
	res.end();
	}
	});
	srv.on('listening', () => { console.log(`http://127.0.0.1:${srv.address().port}/`); })
	srv.listen();
	{
	"type": "module",
	"name": "auth-api-demo",
	"version": "0.1.0",
	"bin": "./index.mjs"
	}