gistfile1.js

var xhr = new XMLHttpRequest({
    mozSystem: true
  });

  // To enable xhr.abort if user cancels
  outReq.xhr = xhr;
  outReq.oncancel = function() {
    this.xhr.abort();
  }

  xhr.open('GET', remote, true);
  xhr.responseType = 'json';

  xhr.timeout = fb.operationsTimeout || fb.DEFAULT_TIMEOUT;

  xhr.onload = function(e) {
    if (xhr.status === 200 || xhr.status === 400 || xhr.status === 0) {
      if (callback && typeof callback.success === 'function')
        self.setTimeout(function() {
          callback.success(xhr.response);
        },0);
    }
    else {
      self.console.error('FB: HTTP error executing query. ',
                         query, ' Status: ', xhr.status);
      if (callback && typeof callback.error === 'function')
        self.setTimeout(callback.error, 0);
    }
  } // onload

  xhr.ontimeout = function(e) {
    self.console.error('FB: Timeout!!! while executing query', query);
    if (callback && typeof callback.timeout === 'function')
      self.setTimeout(callback.timeout, 0);
  } // ontimeout

  xhr.onerror = function(e) {
    self.console.error('FB: Error while executing query: ', query,
                             ': ', e);
    if (callback && typeof callback.error === 'function')
      self.setTimeout(function() {
        callback.error(e);
      },0);
  } // onerror

  xhr.send();