Retrieves the total number of fragments that have been stepped past in a reveal.js presentation.

get-past-fragments.js

function getUniqueFragments( fragmentElements ) {
  return Array.from( fragmentElements )
    .map( ( fragment, i ) => fragment.getAttribute( 'data-fragment-index' ) || i )
    .filter( (value, index, array) => array.indexOf(value) === index ).length;
}

function getPastFragmentCount() {
  const pastSlides = Array.from( Reveal.getSlidesElement().querySelectorAll( 'section.past' ) );

  const fragmentsInPastSlides = pastSlides.reduce( ( total, slide ) => {
    return total + getUniqueFragments( slide.querySelectorAll( '.fragment' ) );
  }, 0 );

  const fragmentsInCurrentSlide = getUniqueFragments( Reveal.getCurrentSlide().querySelectorAll( '.fragment.visible' ) );

  return fragmentsInPastSlides + fragmentsInCurrentSlide;
}

getPastFragmentCount();