Async IF Construct using JQuery Deferred

async_if.js

/* asynchronous IF construct implementation */

async_if = function(fn, args, timeout) {
    var curr_probe, dfd, probe;
    dfd = new jQuery.Deferred();
    curr_probe = null;

    probe = function() {
      if (fn(args)) {
        dfd.resolve(args); /* this will invoke success callback */
        return curr_probe = null;
      } else {
        /* lets return after 5 milliseconds to re-run checker function */
        return curr_probe = setTimeout(probe, 5); 
      }
    };
    if (timeout) {
      /* if this is timeout async operation, return failure if condition is not met within timeout */
      setTimeout(function() {
        curr_probe && clearTimeout(curr_probe);
        return dfd.reject(args);
      }, timeout);
    }
    probe();
    return dfd.promise();
};