Dynamic redirection in expressjs

Am using Keycloak for sso which serves multiple idp autentication and using Express js as my middleware. Here am stuck with dynamic redirection, when i try to login using first tenant credentials am getting preferred-username as empid@domain1.com where as when i try to login with second tenant am getting empid@domain2.com

My query here is how to redirect to different pages based on this preferred_username obtained from response. Example: When i login using 1st tenant i should get redirected to https://example1.com and for second tenant i should get redirected to https://example2.com. How to make it work using if condition? Any help is appreciated. Example code is attached for reference

     var express = require('express');
     var session = require('express-session');
     var bodyParser = require('body-parser');
     var Keycloak = require('keycloak-connect');
     var cors = require('cors');

     app.use(bodyParser.json());

     app.use(cors());

     var memoryStore = new session.MemoryStore();

     app.use(session({
     secret: 'some secret',
     resave: false,
     saveUninitialized: true,
     store: memoryStore
     }));

     var keycloak = new Keycloak({
     store: memoryStore
     });

     app.use(keycloak.middleware({
     logout: '/logout',
     admin: '/'
     }));

     app.get('/Example1', function (req, res) {
     res.redirect('https://example1.com')
     });

     app.get('/Example2', keycloak.protect('realm:user'), function (req, res) {
     res.redirect('https://example2.com')
     console.log(req.kauth.grant.access_token.content.preferred_username)
     });

    app.use('*', function (req, res) {
    res.send('Not found!');
    });