function nicovideo_createPanel(id, labelText) {
  let panelID = 'itab_' + id;

  let label = document.createElement('a');
  label.href = '#' + panelID;
  label.innerHTML = '<div>' + labelText + '</div>';
  // remove extra <a>...</a>
  label.firstChild.textContent = labelText;
  document.querySelector('#itab td').appendChild(label);

  let panel = document.createElement('div');
  panel.id = panelID;
  panel.className = 'info';
  document.querySelector('.info_frm').appendChild(panel);

  unsafeWindow.cont = unsafeWindow.$$('.info_frm .info');
  const act = unsafeWindow.act;
  label.addEventListener('click', function(e) {
    e.preventDefault();
    Array.forEach(document.querySelectorAll('#itab td a'),
                  function(elm) elm.classList.remove(act));
    label.classList.add(act);
    Array.forEach(document.querySelectorAll('.info_frm .info'),
                  function(elm) elm.id === panelID
                  ? elm.classList.add(act)
                  : elm.classList.remove(act));
  }, false);

  return { label: label, panel: panel };
}