Свойство responseText

String? responseText

Ответ в виде строки или пустая строка в случае сбоя.

Реализация

String? get responseText native;

© 2012 the Dart project authors
Licensed under the BSD 3-Clause "New" or "Revised" License.
https://api.dart.dev/stable/2.19.6/dart-html/HttpRequest/responseText.html