Hot reload node module

country.json

[
  "countryA",
  "countryB"
]

server.js

// This file starts a server and listen to port 8989. When you change the module, it'll auto refresh it. 

var fs = require('fs'),
  http = require('http'),
  port = 8989, 
  file = './country.json',
  server, 
  countries = require(file); // requiring here is important. It didn't work when I set `countries = []`. 

fs.watchFile(file, function () {
        delete require.cache[require.resolve(file)];
        countries = require(file);
})

function handleRequest(req, res) {
        res.writeHead(200, {'Content-Type': 'text/plain'});

        res.end(countries.join(', '));
}

server = http.createServer(handleRequest);

server.listen(port, function () {
        console.log('Server listenting to '.concat(port));
})
~

As said on official doc watchFile should be replaced with watch.