overriding the default Event system in favor of a more performant, feature rich event emitter (eventemitter3)

example.js

import EventEmitter from 'eventemitter3'
import pdfjs from 'pdfjs-dist'

const el = document.getElementById('my-viewer')

// create instance of EventEmitter 3
const eventBus = new EventEmitter()

// create a document Viewer and pass our event emitter instance
// see: https://github.com/mozilla/pdfjs-dist/blob/master/web/pdf_viewer.js#L2593
const viewer = pdfjs.PDFViewer({
  container: el,
  eventBus: eventBus
})

// now when the viewer emits an event it emits it on eventemitter isntance, not the DOM element
ee.on('pagechange', function(e) {
  console.log('the page changed', e)
})