const contents = document.querySelectorAll('.content') const listItems = document.querySelectorAll('nav ul li') listItems.forEach((item, idx) => { item.addEventListener('click', () => { hideAllContents() hideAllItems() item.classList.add('active') contents[idx].classList.add('show') }) }) function hideAllContents() { contents.forEach(content => content.classList.remove('show')) } function hideAllItems() { listItems.forEach(item => item.classList.remove('active')) }