index.js

// index.js
require("dotenv").config();

// init express
var express = require("express");
var app = express();

// enable CORS (https://en.wikipedia.org/wiki/Cross-origin_resource_sharing)
var cors = require("cors");
app.use(cors({ optionsSuccessStatus: 200 })); // some legacy browsers choke on 204

// http://expressjs.com/en/starter/static-files.html
app.use(express.static("public"));

// http://expressjs.com/en/starter/basic-routing.html
app.get("/", function (req, res) {
  res.sendFile(__dirname + "/views/index.html");
});

// API endpoint for whoami
app.get("/api/whoami", function (req, res) {
  const ipaddress = req.ip;
  const language = req.headers["accept-language"];
  const software = req.headers["user-agent"];
  res.json({ ipaddress, language, software });
});

// listen for requests
var listener = app.listen(process.env.PORT || 3000, function () {
  console.log("Your app is listening on port " + listener.address().port);
});