--- a
+++ b/docs/lagunita/js/custom.js
@@ -0,0 +1,16 @@
+// Custom Javascript for Lagunita HTML Theme
+// You can add custom JS functions to this file.
+jQuery(document).ready(function($){
+  // Add "active" to nav element if matches body class of "subnav-n"
+  var bodyClass="";
+  var matches = document.body.className.match(/(^|\s+)(subnav-\d+)(\s|$)/);
+  if (matches) {
+    // found the bodyClass
+    bodyClass = matches[2];
+  }
+
+  if (bodyClass.length > 0){
+    var target = $( '#' + bodyClass );
+    target.addClass('active');
+  }
+});
\ No newline at end of file