code: @Override
      public JSObject execute(String command) {
          Object returnValue = engine.executeScript(command);
          if (returnValue instanceof JSObject) {
              return (JSObject) returnValue;
          }
  
          return null;
      }
docs: Execute the specified command returning a value (if any)
  
  @param command The JavaScript command to execute
  @return The underlying JavaScript object that was returned by the script.