function displaySpan() {
  const selection = window.getSelection();
  const caretRect = selection.getRangeAt(0).getClientRects()[0];
  const {height, top, left} = caretRect;
  const span = document.createElement('span');
  const body = document.querySelector('#root');
  span.classList.add('test');
  span.style.width = '1px';
  span.style.position = 'fixed';
  span.style.backgroundColor = 'orangered';
  span.style.height = `${height}px`;
  span.style.top = `${top}px`;
  span.style.left = `${left}px`;
  body.appendChild(span);
}

function hideSpan() {
  const span = document.querySelector('.test');
  span?.remove();
}