polling using jQuery deferred with timeout, similar to go channels

polling.js

/* Performs a pooling with a timeout limit and throttle frequency.

  fn - a function that returns a promise of an async computation
  timeout - time in milliseconds to cancel pooling (default 10s)
  throttle - the minimumm time between pollings

  Use throttle if the async computation is too fast and you want
  that occurrances happens in intervals.
*/
var polling = function(fn, timeout, throttle) {
  var expired = false; // guard

  timeout = timeout || 10000; // default timeout of 10s
  throttle = throttle || 1000; // 1s sample at least

  return $.Deferred(function(dfd) {
    // stop pooling if timeout
    setTimeout(function() {
      expired = true;
      // we consider the deferred as completed
      dfd.resolve();
    }, timeout);

    // the pooler that will call the deferred function
    var pooler = _.throttle(function() {
      // TODO: the fn should be compliant with the done and progress?
      fn().done(function(result) {
        // once the async computation it need to inform if the job is complete
        if (expired || result.complete) {
          dfd.resolve();
        } else {
          // notifies progress
          dfd.notify(result.time);
        }
      }).always(function() {
        if (!expired) {
          pooler(); // recur
        }
      });
    }, throttle);

    pooler(); // start pooler

    return dfd.promise();
  });
};


polling(getQuote, 30000).progress(updateHtml).done(removeLoader);