app/views/json/enumeration/themes.erb
"themes": {
<% unless @themes.empty? -%>
<% last_index = @themes.size - 1 -%>
<% @themes.each_with_index do |theme, index| -%>
<%= theme.slug.to_json %>: {
<%= render('@theme', theme: theme) -%>
}<% unless index == last_index -%>,<% end -%>
<% end -%>
<% end -%>
},