mongoose-and-koa-with-ee.js

const EventEmitter = require('events');

const Koa = require('koa');
const mongoose = require('mongoose');

// Excerpted from https://nodejs.org/dist/latest-v8.x/docs/api/events.html#events_events
class MyEmitter extends EventEmitter {}
const myEmitter = new MyEmitter();

// Excerpted from https://mongoosejs.com/docs/index.html
mongoose.connect('mongodb://localhost/test');
var db = mongoose.connection;
db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', function() {
  // we're connected!

  const Role = mongoose.model('Role', {
    name: String,
    rules: Object,
  });

  myEmitter.emit('loadAbilities');
});

const abilities = {};

myEmitter.once('loadAbilities', () => {
  // TODO Load abilities and emit 'startListening'
  const roles = mongoose.models.Role.find({});

  roles.forEach((role) => {
    abilities[role.name] = role.rules;
  });
});

// Excerpted from https://koajs.com/#application
const app = new Koa();

app.use(async (ctx) => {
  ctx.body = 'Hello World';
});

myEmitter.once('startListening', () => {
  app.listen(3000);
});