diff --git a/javascripts/demo.js b/javascripts/demo.js
index 0905c22..38fc6a8 100644
--- a/javascripts/demo.js
+++ b/javascripts/demo.js
@@ -11,5 +11,12 @@ $(document).ready(function() {
 		revert: "invalid",
 		helper: "clone"
 	});
+
+  $(".fs").on("sortupdate", function() {
+      $(this).attr("data-content", $(this).fsortable("capacity"));
+  }).each(function() {
+      // Set the initial value of the attribute.
+      $(this).attr("data-content", $(this).find(".fsortable-empty").length);
+  });
 });