src/jdk/nashorn/internal/parser/JSONParser.java

*** 347,356 ****
--- 347,360 ----
                  result = LiteralNode.newInstance(arrayToken, finish, elements);
                  break loop;
  
              case COMMARIGHT:
                  next();
+                 // check for trailing comma - not allowed in JSON
+                 if (type == RBRACKET) {
+                     throw error(AbstractParser.message("trailing.comma.in.json", type.getNameOrType()));
+                 }
                  break;
  
              default:
                  // Add expression element.
                  elements.add(jsonLiteral());
*** 386,395 ****
--- 390,403 ----
                  next();
                  break loop;
  
              case COMMARIGHT:
                  next();
+                 // check for trailing comma - not allowed in JSON
+                 if (type == RBRACE) {
+                     throw error(AbstractParser.message("trailing.comma.in.json", type.getNameOrType()));
+                 }
                  break;
  
              default:
                  // Get and add the next property.
                  final PropertyNode property = propertyAssignment();