(function () {
  var articleImage = document.querySelectorAll('.article img'),
    nextArrow = document.getElementById('#nextArrow'),
    previousArrow = document.getElementById('prevArrow');
  
  articleImage.addEventListener('click', openGallery);
  nextArrow.addEventListener('click', showNextImage)
  previousArrow.addEventListener('click', showPreviousImage)
  
  function openGallery() {
    //...
  }
  
  function showNextImage() {
    //...
    
  }
  
  function showPreviousImage() {
    //...
  }
  
  
  
})();