Fixed editItem method

app.snippet.4.js

addNewItem(itemName) {
  //...

  item.getElementsByClassName('edit-button')[0].addEventListener('click', () => this.editItem(item));
}

editItem(item) {
  const oldItemName = item.getElementsByClassName('item-name')[0].innerHTML.trim();

  const editInput = htmlToElement(`
    <input type="text" value="${oldItemName}" placeholder="Enter new item name" class="bg-gray-800 px-4 py-2 rounded block w-full text-gray-200 font-light">
  `);

  editInput.addEventListener('keyup', e => {
    if (e.keyCode === 13) {
      this.performEdit(item, editInput)
    }
  });

  const itemNameEl = item.getElementsByClassName('item-name')[0];
  const editButtonEl = item.getElementsByClassName('edit-button')[0];

  insertElementAfter(editInput, itemNameEl);

  itemNameEl.classList.add('hidden');
  editButtonEl.classList.add('hidden');
}