Why does the server give an error when trying to go back a folder?

Question

Express.js

How to make a root directory, which is the parent folder of the folder in which we have a server file?
Such code throws an error, like others with attempts to get into the folder before.

const app = express();
app.use(express.static('../public'));
app.get('/', function (req: Request, res: Response) {
  res.sendFile(`${__dirname}/../public/index.html`);
});

Answer 1

res.sendFile('index.html', { root:  path.resolve(__dirname, '../public/index.html') })