server.js

const koa = require('koa');
const app = koa();
const port = process.env.PORT || 1337;

var deku = require('deku');
var tree = deku.tree;
var element = deku.element;
var renderString = deku.renderString;
var Counter = require('./lib/counter');

app.use(function *(){
  function doSomething() {
    console.log('I did something.');
  }

  let counter = tree(
    element(Counter, { onAnEmittedEventFromCounter: doSomething })
  );

  this.body = renderString(counter);
});

let server = app.listen(port, function() {
  console.log('Koa is listening to http://localhost:' + port);
});