server.js

const express = require('express')
const server = express()

/* route requests for static files to appropriate directory */
server.use('/public', express.static(__dirname + '/public'), function (req, res, next){
  res.setHeader("Access-Control-Allow-Origin", "*");
    // Request headers you wish to allow
    res.setHeader("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
    // Set to true if you need the website to include cookies in the requests sent
    res.setHeader('Access-Control-Allow-Credentials', true);
    // Pass to next layer of middleware
    next();
});

/* other routes defined before catch-all */
server.get('/some-route', (req, res) => {
  res.setHeader('Access-Control-Allow-Origin', '*');
    res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS, PUT, PATCH, DELETE'); // If needed
    res.setHeader('Access-Control-Allow-Headers', 'X-Requested-With,content-type'); // If needed
    res.setHeader('Access-Control-Allow-Credentials', true); // If needed

  res.send('ok')
})

/* final catch-all route to index.html defined last */
server.get('/', (req, res) => {
  res.setHeader('Access-Control-Allow-Origin', '*');
    res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS, PUT, PATCH, DELETE'); // If needed
    res.setHeader('Access-Control-Allow-Headers', 'X-Requested-With,content-type'); // If needed
    res.setHeader('Access-Control-Allow-Credentials', true); // If needed

  res.sendFile(__dirname + '/public/index.html');
})

const port = 8000;
server.listen(port, function() {
  console.log('server listening on port ' + port)
})