let id = RANGE_END; id < LENGTH; id++)
    list[id] = {id, text: `R${Math.random()}`};
  console.time('change-end');
  $(document.body, ul);
  console.timeEnd('change-end');
  next();
}

function reverse(next) {
  list = list.reverse();
  console.time('reverse');
  $(document.body, ul);
  console.timeEnd('reverse');
  next();
}

function addStart(next) {
  for (let id = 0; id < RANGE_START; id++)
    list.unshift({id, text: `R${Math.random()}`});
  console.time('add-start');
  $(document.body, ul);
  consol