QuerySelectorAll и элемент на котором есть фокус

function nav (move) {
  var next = currentIndex + move;
  var items = document.querySelectorAll('.items');
  var targetElement = items[next];
  targetElement.focus();
}

var currentIndex = document.querySelector('.items');

<div class="items">1</div>
<div class="items">2</div>
<div class="items">3</div>
<div class="items">4</div>
<input type="text" class="items"/>
<a href="more.html" clas="items">more..</a>

<div class="items" tabIndex="1"></div>

document.activeElement.addEventListener('keydown', handleKeydownEvent);

function handleKeydown(e) {
  switch(e.key) {
    case 'ArrowUp':
      nav(-1);
      break;
    case 'ArrowDown':
      nav(1);
      break;
    case 'ArrowRight':
      nav(1);
      break:
    case 'ArrowLeft': 
      nav(-1);
      break;
  }
}

function nav (move) {
  var next = currentIndex + move;
  var items = document.querySelectorAll('.items');
  var targetElement = items[next];
  targetElement.focus();
}

function nav (move) {
  var currentIndex = document.activeElement.tabIndex;
  var next = currentIndex + move;
  var items = document.querySelectorAll('.items');
  var targetElement = items[next - 1];
  targetElement.focus();
}