如何在Dart HttpRquest帖子中访问响应数据

Question

html：

<div>
    <form #form enctype="multipart/form-data">
        <input id ="uploadId" type="file"   #upload name='uploadingFiles' (change)="uploadFiles(form)"  multiple>
    </form>
    <span>{{progress}}</span>
</div>

飞镖：

import 'dart:html';

void uploadFiles(form) {
  var formData = new FormData(form);
  final request = new HttpRequest();
  request.open('POST', 'http://localhost/uploadfiles');

  request.upload.onProgress.listen((ProgressEvent e) {
    progress = (e.loaded * 100 / e.total).toInt().toString() + '%';
  });

  request.onReadyStateChange.listen((e) {
    print('Uploaded');
  }, onDone: () {
    //  Gives  correct status sent by the server. e.g. 415 in case of  unsupported  media  type
    print("loaded " + request.status.toString());
  }, onError: (e) {
    print('err' + e.toString());
  });

  request.send(formData);
}

如上所述，我可以获得httpStatus错误代码。我还如何访问服务器发送的错误文本，即响应json对象？

是否存在使用await和async的替代API，从而可以访问

1. httpStatusCode和响应文本
2. 它也可以发送进度事件以显示文件上传状态