How to make redirects in nodejs?

Question

Node.js

Hello.
I have a vue + ssr app
Actually ssr itself provides a node server.
On it I try to make the redirects I need.
The first one is a 301 redirect from a url with a slash to a url without a slash.
Tried to do so

const fullUrl = req.protocol + '://' + req.get('host') + req.originalUrl;
const stripTrailingSlash = url => url.replace(/\/$/, "");
const urlArray = fullUrl.split('');

res.setHeader("Content-Type", "text/html");
res.setHeader("Server", serverInfo);

if (urlArray[urlArray.length - 1] === '/') {
    res.writeHead(301, {'Location': stripTrailingSlash(fullUrl)});
    res.end();
}

But something is clearly not right here, when loading the page, first I see an empty page, and then the right one.
I also have application localization.
There are 2 locales, eg /en, /ru
I want to make it so that if there is no locale in the url, eg domain.com, then do a 301 redirect to domain.com/ru
I roughly understand how to write it, but if you do a redirect, then in the console it says that the number of redirects
has been exceeded