Random shuffle for image galleries

example.tpl

<!-- Content with image gallery field called "image_gallery" -->
<pop:content>
  <pop:random:gallery field="image_gallery">
    <pop:value resize="fill" width="200"/>
  <pop:random:gallery>
</pop:content>

random.js

var shuffle = function(images) {
  var a = [images[0]];
  var i = 1;
  while (images[i]) {
    var j = Math.floor(Math.random() * (i + 1));
    a[i] = a[j];
    a[j] = images[i];
    i++;
  }
  return a;
};

exports.gallery = function(options, _, scope) {
  var gallery = scope[options.field].images;
  
  return gallery.length ? shuffle(gallery) : [];
}