Firebase paging

loadMore

var loadMore = (ref, from, qty, reverse=false)=> {
  var direction = reverse ? 'endAt' : 'startAt';
  return ref['direction'](null,from)
  .limitToFirst(qty+1)
  .once('value')
  .then((snap)=>{
    var items = snap.val() || {};
    var res = {hasMore:false, items};
    delete items[from];
    res.hasMore = Object.keys(items).length == qty;
    return res
  })
}