index.js

const express = require('express');
const redis = require('redis');

const app = express();

const client = redis.createClient({
    host: "redis-server",   // Hostname for Redis Server. This name comes from "docker-compose.yml" file. Docker will automatically tells Express to use redis-server container.
    port: 6379              // Default Redis Port
});
client.set('visits', 0);

app.get('/', (req, res) => {
    client.get('visits', (err, visits) => {
        res.send('Number of visits is ' + visits);
        client.set('visits', parseInt(visits) + 1);
    })
});

app.listen(8080, () => {
    console.log('Listening on port 8080');
});