text: const sidebarBox = document.querySelector('#box'),
      sidebarBtn = document.querySelector('#btn');
  
  if (sidebarBtn != null) {
      sidebarBtn.addEventListener('click', event => {
          sidebarBtn.classList.toggle('active');
          sidebarBox.classList.toggle('active');
      });
  }
  
  if (window != null) {
      window.addEventListener('keydown', event => {
          if (sidebarBox.classList.contains('active') && event.keyCode === 27) {
              sidebarBtn.classList.remove('active');
              sidebarBox.classList.remove('active');
          }
      });
  };