Пытаюсь сделать слайдер на js

var array = ['1.jpg', '2.jpg', '3.png', '4.jpg'], 
  section = document.getElementById('section'), 
  next = document.getElementById('next'), 
  back = document.getElementById('back'); 
 
 
next.addEventListener('click', function() { 
  var current = +section.getAttribute('data-current'); 
  current++; 
  if (current >= array.length) { 
    current = 0; 
  } 
  section.setAttribute('data-current', current); 
  section.innerHTML = array[current]; 
}); 
 
back.addEventListener('click', function() { 
  var current = +section.getAttribute('data-current'); 
  current--; 
  if (current < 0) { 
    current = array.length - 1; 
  } 
  section.setAttribute('data-current', current); 
  section.innerHTML = array[current]; 
});

<button id="back">back</button> 
<button id="next">next</button> 
<br /> 
<div id="section" data-current="0">1.jpg</div>