hugo-snap-gallery/static/js/snap-gallery.js

// Variables
var baseid = "snap-lightbox-";
var imageIndex = 1;

// Open the Lightbox
function openLightbox(id) {
  document.getElementById(baseid + id).style.display = "block";
}

// Close the Lightbox
function closeLightbox(id) {
  document.getElementById(baseid + id).style.display = "none";
}

// Next/previous controls
function moveLightboxItem(id, n) {
  showLightboxItem(id, imageIndex += n);
}

// Move lightbox to the specified item
function openLightboxItem(id, n) {
  showLightboxItem(id, imageIndex = n);
}

// Make a specific image visible, make others hidden
function showLightboxItem(id, n) {
  var i;
  var lightbox = document.getElementById(baseid + id);
  var images = lightbox.querySelectorAll(".snap-lightbox-inner");
  if (n > images.length) { imageIndex = 1 }
  if (n < 1) { imageIndex = images.length }
  for (i = 0; i < images.length; i++) {
    images[i].style.display = "none";
  }
  images[imageIndex - 1].style.display = "inline-block";
}