document.body.append(document.createElement('textarea'));
document.body.append(document.createElement('button'));

document.querySelector('button').addEventListener('click', function () {
  const text = document.querySelector('textarea').textContent;
  const lowerCase = text.toString().toLowerCase();
  console.log(lowerCase);
});

I am sorry if I don't display stuff properly here, I'm new to this place, and fairly new to coding but trying to figure out stuff.