reveal-js-base-theme/js/slidenotes.js

(function() {
  // don't emit events from inside the previews themselves
  var qs = window.location.href.split('?');
  if (qs.length > 1 && qs[1].match('receiver')) { return; }

  var socket = io.connect(window.location.origin);
  var socketId = socket.socket.sessionid;
  console.log('View slide notes at ' + window.location.origin + '/_notes/' + socketId);

  Reveal.addEventListener( 'slidechanged', function( event ) {
    var nextindexh;
    var nextindexv;
    var slideElement = event.currentSlide;

    if (slideElement.nextElementSibling && slideElement.parentNode.nodeName == 'SECTION') {
      nextindexh = event.indexh;
      nextindexv = event.indexv + 1;
    } else {
      nextindexh = event.indexh + 1;
      nextindexv = 0;
    }

    var notes = slideElement.querySelector('aside.notes');
    var slideData = {
      notes : notes ? notes.innerHTML : '',
      indexh : event.indexh,
      indexv : event.indexv,
      nextindexh : nextindexh,
      nextindexv : nextindexv,
      socketId : socketId
    };

    socket.emit('slidechanged', slideData);
  } );
}());