var xhr = new XMLHttpRequest();
xhr.open('GET', '/server', true);

//  , responseType      "document"
xhr.responseType = 'document';

// overrideMimeType()   ,      XML
xhr.overrideMimeType('text/xml');

xhr.onload = function () {
  if (xhr.readyState === xhr.DONE) {
    if (xhr.status === 200) {
      console.log(xhr.response);
      console.log(xhr.responseXML);
    }
  }
};

xhr.send(null);










 if (this.readyState == 4 && this.status == 200) {