mustache.js in_groups_of I needed mustache.js to iterate over a list in groups of 2 to take advantage of Twitter Bootstraps “row” and “span” classes. Here is how I got it done (using jQuery).

gistfile1.js

$.fn.inGroupsOf = function( countPerGroup, groupName ) {
  var groups = [], offset = 0, $group, jsonOptions;
  while ( ($group = this.slice( offset, (countPerGroup + offset) )).length ) {
      jsonOptions = {};
      jsonOptions[groupName] = $group.toArray();
      groups.push( jsonOptions );
      offset += countPerGroup;
  }
  return groups;
};

      
var renderEmailImageCategories = function(email_image_categories){
  $.each(email_image_categories, function(index, email_image_category) {
    email_image_category.image_groups = function() {
      return $(this.images).inGroupsOf(2,'images');
    };
  });
  template = $.mustache('{{#email_image_categories}}<h4>{{name}}{{^name}}My Images{{/name}}</h4>{{#image_groups}}<div class="row">{{#images}}{{#.}}<a href="#" class="email_image_link" data- data-url="{{file.span3.url}}"><img src="{{file.span3.url}}" class="span3"  /></a>{{/.}}{{/images}}</div>{{/image_groups}}{{/email_image_categories}}',{"email_image_categories": email_image_categories});
  $('#custom_email_image_body').html(template);
};