Future<HttpRequest> request(String url, { String method, bool withCredentials, String responseType, String mimeType, Map<String, String> requestHeaders, sendData, void onProgress(ProgressEvent e) })

Creates and sends a URL request for the specified url.

By default request will perform an HTTP GET request, but a different method (POST, PUT, DELETE, etc) can be used by specifying the method parameter. (See also HttpRequest.postFormData for POST requests only.

The Future is completed when the response is available.

If specified, sendData will send data in the form of a ByteBuffer, Blob, Document, String, or FormData along with the HttpRequest.

If specified, responseType sets the desired response format for the request. By default it is String, but can also be 'arraybuffer', 'blob', 'document', 'json', or 'text'. See also HttpRequest.responseType for more information.

The withCredentials parameter specified that credentials such as a cookie (already) set in the header or authorization headers should be specified for the request. Details to keep in mind when using credentials:

  • Using credentials is only useful for cross-origin requests.
  • The Access-Control-Allow-Origin header of url cannot contain a wildcard (*).
  • The Access-Control-Allow-Credentials header of url must be set to true.
  • If Access-Control-Expose-Headers has not been set to true, only a subset of all the response headers will be returned when calling getAllRequestHeaders.

The following is equivalent to the getString sample above:

var name = Uri.encodeQueryComponent('John');
var id = Uri.encodeQueryComponent('42');
HttpRequest.request('users.json?name=$name&id=$id')
  .then((HttpRequest resp) {
    // Do something with the response.
});

Here's an example of submitting an entire form with FormData.

var myForm = querySelector('form#myForm');
var data = new FormData(myForm);
HttpRequest.request('/submit', method: 'POST', sendData: data)
  .then((HttpRequest resp) {
    // Do something with the response.
});

Note that requests for file:// URIs are only supported by Chrome extensions with appropriate permissions in their manifest. Requests to file:// URIs will also never fail- the Future will always complete successfully, even when the file cannot be found.

See also: authorization headers.

Source 

static Future<HttpRequest> request(String url,
    {String method,
    bool withCredentials,
    String responseType,
    String mimeType,
    Map<String, String> requestHeaders,
    sendData,
    void onProgress(ProgressEvent e)}) {
  var completer = new Completer<HttpRequest>();

  var xhr = new HttpRequest();
  if (method == null) {
    method = 'GET';
  }
  xhr.open(method, url, async: true);

  if (withCredentials != null) {
    xhr.withCredentials = withCredentials;
  }

  if (responseType != null) {
    xhr.responseType = responseType;
  }

  if (mimeType != null) {
    xhr.overrideMimeType(mimeType);
  }

  if (requestHeaders != null) {
    requestHeaders.forEach((header, value) {
      xhr.setRequestHeader(header, value);
    });
  }

  if (onProgress != null) {
    xhr.onProgress.listen(onProgress);
  }

  xhr.onLoad.listen((e) {
    var accepted = xhr.status >= 200 && xhr.status < 300;
    var fileUri = xhr.status == 0; // file:// URIs have status of 0.
    var notModified = xhr.status == 304;
    // Redirect status is specified up to 307, but others have been used in
    // practice. Notably Google Drive uses 308 Resume Incomplete for
    // resumable uploads, and it's also been used as a redirect. The
    // redirect case will be handled by the browser before it gets to us,
    // so if we see it we should pass it through to the user.
    var unknownRedirect = xhr.status > 307 && xhr.status < 400;

    if (accepted || fileUri || notModified || unknownRedirect) {
      completer.complete(xhr);
    } else {
      completer.completeError(e);
    }
  });

  xhr.onError.listen(completer.completeError);

  if (sendData != null) {
    xhr.send(sendData);
  } else {
    xhr.send();
  }

  return completer.future;
}