Image Swapping with Custom Code

Design help Custom code
1

So, I’m trying to create a custom lightbox modal. I have a main center piece image and tiny thumbnails. I just want to swap out the image source when the thumbnails are clicked. However, I can’t figure out why this is not running? Any ideas?

<script>
var lightboxImage = '';
$('.photo-strip-item').on('click', function(){
	$('.photo-strip-item').removeClass('active');
  $(this).addClass('active');
  lightboxImage = $(this).find('img').attr('src');
  $('.lightbox-image').attr('src', lightboxImage);
});

</script>

Here is my site Read-Only: LINK
(how to share your site Read-Only link)