Redirect non-www and HTTP to www and HTTPS

I am running an Express web server. I used Let's Encypt to create SSL certificates for both the www and non-www version of my domain. My DNS has these records:

CNAME | Host: @   | Target: dynamicdns.example.com. | TTL: 60min
CNAME | Host: www | Target: dynamicdns.example.com. | TTL: 60min

I also have this node.js code to run the webserver:

// Dependencies
const express = require('express');
const fs = require('fs');
const http = require('http');
const https = require('https');

// Create express instance
const app = express();

// Get credentials from system
const privateKey = fs.readFileSync('/etc/letsencrypt/live/www.example.com/privkey.pem', 'utf8');
const certificate = fs.readFileSync('/etc/letsencrypt/live/www.example.com/cert.pem', 'utf8');
const ca = fs.readFileSync('/etc/letsencrypt/live/www.example.com/chain.pem', 'utf8');
const credentials = {
    key: privateKey,
    cert: certificate,
    ca: ca
};

// Initalize server
app.use(express.static('public'));
const httpServer = http.createServer(app);
const httpsServer = https.createServer(credentials, app);

// Listen for HTTP
httpServer.listen(80, () => {
    console.log('HTTP Server running on port 80');
});

// Listen for HTTPS
httpsServer.listen(443, () => {
    console.log('HTTPS Server running on port 443');
});

This all works correctly, but it creates an issue with having multiple valid URLs for the same content. The following URLs are all valid right now:

http://example.com
http://www.example.com
https://example.com
https://www.example.com

I want to redirect all the wrong URLs to https://www.example.com, which is the correct URL. I'm not sure how I should go about doing this. Any help would be appreciated.

from Redirect non-www and HTTP to www and HTTPS