Simple event aggregator using Lodash

event-aggregator.js

const _ = require('lodash');
const colors = require('colors/safe');
const EventEmitter = require('events').EventEmitter;

const ev = new EventEmitter();

const predicate = ['q3', 'q6', 'q9'];

let agg = {};

ev.on('query.event', (event) => {

  agg[event.id] = event;

  const resolved = _.every(predicate, _.partial(_.has, agg));

  console.log(colors.gray(event));

  if (resolved) {
    const results = _.values(_.pick(agg, predicate));
    const condition = _.every(results, o => { return o.value >= 5 && o.value <= 8; });

    if (condition) {
      console.log(colors.yellow(`predicate condition resolved`));
      console.log(colors.green(JSON.stringify(results, null, 2)));
      // agg = {};
    }
  }

});

setInterval(() => {
  ev.emit('query.event', { id: 'q' + _.random(1, 10), value: _.random(1, 10), timestamp: new Date().toISOString() });
}, 100);