https://www.terrypratchettbooks.com/wp-content/themes/pratchett-2019/js/captions.js

1jQuery(document).ready(function( $ ) {
2    
3    var caption_array = [];
4    $("[data-caption]").each(function(){
5        var caption = $(this).attr('data-caption');
6        if (caption !== '') {
7            caption_array.push(caption);
8        }
9    }) 
10    
11    if (caption_array !== undefined && caption_array.length !== 0) {
12        
13        var caption_array_sort = caption_array.sort();
14        var caption_array_unique = $.unique(caption_array_sort);
15
16        $(caption_array_unique).each(function() {
17            
18            $( '.caption__images ul' ).append( '<li>' + this + '</li>' );
19            
20        })
21        
22    } else {
23        $('.captions-block').hide();
24    }
25    
26});