wallabag/app/Resources/static/themes/_global/js/restoreScroll.js

function supportsLocalStorage() {
  try {
    return 'localStorage' in window && window.localStorage !== null;
  } catch (e) {
    return false;
  }
}

function savePercent(id, percent) {
  if (!supportsLocalStorage()) { return false; }
  localStorage['wallabag.article.' + id + '.percent'] = percent;
  return true;
}

function retrievePercent(id) {
  if (!supportsLocalStorage()) { return false; }

  var bheight = $(document).height();
  var percent = localStorage['wallabag.article.' + id + '.percent'];
  var scroll = bheight * percent;

  $('html,body').animate({ scrollTop: scroll }, 'fast');

  return true;
}