code: function (name) {
              var match, responseHeaders, self = this;    // ie8 will be lowercase for content-type
              // ie8 will be lowercase for content-type
              name = name.toLowerCase();
              if (self.state === 2) {
                  if (!(responseHeaders = self.responseHeaders)) {
                      responseHeaders = self.responseHeaders = {};
                      while (match = HEADER_REG.exec(self.responseHeadersString)) {
                          responseHeaders[match[1].toLowerCase()] = match[2];
                      }
                  }
                  match = responseHeaders[name];
              }
              return match === undefined ? null : match;
          }
docs: get header value in response to specified header name
  @param {String} name header name
  @return {String} header value
  @member KISSY.IO