zoneminder/web/skins/classic/views/js/controlpreset.js

function updateLabel() {
  var form = $('contentForm');
  var preset_ddm = form.elements['preset'];

  var presetIndex = preset_ddm[preset_ddm.selectedIndex].value;
  if ( labels[presetIndex] ) {
    form.newLabel.value = labels[presetIndex];
  } else {
    form.newLabel.value = '';
  }
}
window.addEventListener('DOMContentLoaded', updateLabel);