AJAX wrapped in Q as an AMD module with `expect` option.

qxhr.amd.js

define(['q'], function(Q){

  return function(options) {
    var deferred = Q.defer()
      , req = new XMLHttpRequest();

    req.open(options.method || 'GET', options.url, true);

    // Set request headers if provided.
    Object.keys(options.headers || {}).forEach(function (key) {
      req.setRequestHeader(key, options.headers[key]);
    });

    req.onreadystatechange = function(e) {
      if(req.readyState !== 4) {
        return;
      }

      if([200,304].indexOf(req.status) === -1) {
        deferred.reject(new Error('Server responded with a status of ' + req.status));
      } else {
        options.expect = options.expect || 'anything';
        switch(options.expect.toLowerCase()){
          case 'json':
            deferred.resolve(JSON.parse(e.target.responseText));
            break;
          case 'xml':
            deferred.resolve(e.target.responseXML);
            break;
          default:
            deferred.resolve(e.target.responseText);
            break;
        }
      }
    };

    req.send(options.data || void 0);

    return deferred.promise;
  }

});