file-download-sample.txt

var filename = "";
var type = xhr.getResponseHeader('Content-Type');
var blob = new Blob([response], {type: type});

var URL = window.URL || window.webkitURL;
  var downloadUrl = URL.createObjectURL(blob);

  if (filename) {
    // use HTML5 a[download] attribute to specify filename
    var a = document.createElement("a");
    // safari doesn't support this yet
    if (typeof a.download === 'undefined') {
      window.location = downloadUrl;
    } else {
      a.href = downloadUrl;
      a.download = filename;
      document.body.appendChild(a);
      a.click();
    }
  } else {
    window.location = downloadUrl;
  }

  setTimeout(function () {
    URL.revokeObjectURL(downloadUrl);
  }, 100); // cleanup