e.timeEnd('add-start');
  next();
}

function addMiddle(next) {
  const middle = [];
  for (let id = 0; id < RANGE_START; id++)
    middle.push({id, text: `R${Math.random()}`});
  list.splice(RANGE_START, 0, ...middle);
  console.time('add-middle');
  $(document.body, ul);
  console.timeEnd('add-middle');
  next();
}

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