code: protected <T> T invokeJavascriptReturnValue(String function, Class<T> returnType, Object... args) {
          Object returnObject = invokeJavascript(function, args);
          if (returnObject != null) {
              return (T) returnObject;
          } else {
              return null;
          }
      }
docs: Invoke the specified JavaScript function in the JavaScript runtime.
  
  @param <T>
  @param function The function to invoke
  @param returnType The type of object to return
  @param args Any arguments to pass to the function
  @return The result of the function.