Problem configuring Express

Hello! I am trying to configure Express on my Nginx server, but the terminal hangs on me after trying to run the script. I have a file in the same directory as my index.html (/var/www/html) called script.js that I am trying to run. Here is the code:

var express = require('express');
var app = express();
app.get('/', function (req, res) {
  res.status(200).send('ok');
});
var server = app.listen(3000, 'MY_DROPLET_IP', function () {
  var port = server.address().port;
  console.log('Example app listening at port %s', port);
});
module.exports = server;

When I type node script.js, “example app listening” and all that jazz comes up in the terminal, but then I can’t type anything else, and going to MY_DROPLET_IP:3000 does not display anything except a Chrome error page. Please help!