proxy_server

const proxies = {
  'useragent1': 'http://proxyusername1:proxypassword1@proxyhost1:proxyport1',
  'useragent2': 'http://proxyusername2:proxypassword2@proxyhost2:proxyport2',
  'useragent3': 'http://proxyusername3:proxypassword3@proxyhost3:proxyport3',
};

const server = new ProxyChain.Server({
  port: 8000,
  prepareRequestFunction: ({request}) => {
    const userAgent = request.headers['user-agent'];
    const proxy = proxies[userAgent];
    return {
      upstreamProxyUrl: proxy,
    };
  });
});

server.listen(() => console.log('proxy server started'));