gif-gallery.js

  const right = document.getElementById('buttonRight')
  right.addEventListener('click', slideRight);

  function slideRight() {
    let myCurrent = document.getElementById(positionArray.indexOf(position) + 1);
    myCurrent.classList.remove('current')
    position += imageWidth;
    position %= images * imageWidth;
    gallery.querySelector('#gallery-inner').style.marginLeft = '-' + position + 'px';
    myCurrent = document.getElementById(positionArray.indexOf(position) + 1);
    myCurrent.classList.add('current')
  }