ect attributes, not the
        // elements with those names.
        this.request.url = this._form.getAttribute('action');
        this.request.method = this._form.getAttribute('method') || 'GET';
        this.request.contentType = this._form.getAttribute('enctype') || 'application/x-www-form-urlencoded';
        this.request.withCredentials = this.withCredentials;
        this.request.headers = this.headers;

        if (this._form.method.toUpperCase() === 'POST') {
          this.request.body = json;
   