node.js http-proxy redirect

我如何在node.js中使用http代理模块遵循重定向，以便我可以在浏览器中保持相同的url ?

我有两个网站(a和B)背后的反向代理，用户访问网站a通过反向代理完美，但有一个在网站a到网站B，使url在浏览器更改到网站B，它应该仍然显示在浏览器中的反向代理url

这是我当前的代码

var port = process.env.PORT;
var http = require('follow-redirects').http,
    httpProxy = require('http-proxy'),
    url = require('url');
// http Server 
var proxy = new httpProxy.createServer({});
var httpServer = http.createServer(function (req, res) {
    console.log('request received: ' + req.path);    
    var target = 'http://siteA/';
    if (!req.url.toString().endsWith('/')) {
        target = target + '/';
    }
    if (req.url.toString() != '/') {
        target = target + req.url;
    }
    console.log('routing request to ' + target);
    var urlObj = url.parse(req.url);
    req.headers['host'] = urlObj.host;
    req.headers['url'] = urlObj.href;
    proxy.proxyRequest(req, res, {
        host: urlObj.host,
        target: target,
        enable: { xforward: true }
    }); 
});
httpServer.listen(port);
console.log("server listening at port: " + port);
String.prototype.endsWith = function (s) {
    return this.length >= s.length && this.substr(this.length - s.length) == s;
}
String.prototype.startsWith = function (str) {
    return this.indexOf(str) == 0;
};