Issue #3344199: Collapsible javascript event attach multiple times

js/collapsible.js

@@ -43,18 +43,20 @@
         });
       });
 
-      $('.views_tree_link a', context).on('click', function (e) {
-        e.preventDefault();
-        const $parent = $(this).parent();
-        const $itemList = $parent.parent().children('.item-list');
-
-        const isExpanded = $parent.hasClass('views_tree_link_expanded');
-
-        $itemList.slideToggle();
-        $parent.toggleClass(
-          'views_tree_link_expanded views_tree_link_collapsed',
-        );
-      });
+      $('.views_tree_link a:not(.view-tree-processed)', context)
+        .addClass('view-tree-processed')
+        .on('click', function (e) {
+          e.preventDefault();
+          const $parent = $(this).parent();
+          const $itemList = $parent.parent().children('.item-list');
+
+          const isExpanded = $parent.hasClass('views_tree_link_expanded');
+
+          $itemList.slideToggle();
+          $parent.toggleClass(
+            'views_tree_link_expanded views_tree_link_collapsed',
+          );
+        });
     },
   };
 })(jQuery, Drupal);