ajax-gallery-lightbox.js

<script>  
jQuery(document).on('divi_filter_completed', function(){
    $et_post_gallery = jQuery( '.et_post_gallery' );
   $et_post_gallery.each(function() {
       jQuery(this).magnificPopup( {
         delegate: '.et_pb_gallery_image a',
         type: 'image',
         removalDelay: 500,
         gallery: {
           enabled: true,
           navigateByImgClick: true
         },
         mainClass: 'mfp-fade',
         zoom: {
           enabled: ! et_pb_custom.is_builder_plugin_used,
           duration: 500,
           opener: function(element) {
             return element.find('img');
           }
         }
       } );
   });
});
</script>