write module source code to file and then load as node module

async.js

var http = require('http');
var fs = require('fs');

var helloModuleString = "exports.world = function() { return 'Hello World\\n'; }";
fs.writeFile('./hello.js', helloModuleString, function (err) {
  if (err) return console.log(err);
  var hello = require('./hello');

  http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end(hello.world());
  }).listen(1337, '127.0.0.1');

console.log('Server running at http://127.0.0.1:1337/');
});

sync.js

var http = require('http');
var fs = require('fs');

var helloModuleString = "exports.world = function() { return 'Hello World\\n'; }";
fs.writeFileSync('./hello.js', helloModuleString);
var hello = require('./hello');

http.createServer(function (req, res) {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end(hello.world());
}).listen(1337, '127.0.0.1');

console.log('Server running at http://127.0.0.1:1337/');