Snippet - Multi-thread queue with jq's promises

snippet01.js

{
	// .....

	enqueue: function(items, get_promise, num_threads){
		num_threads = num_threads || 1;
		var dfd = $.Deferred(), i = 0, num_total = items.length, num_active = 0, num_done = 0,
			next = function(){
				while (num_active < num_threads && i < num_total) {
					num_active++;
					get_promise(items[i++]).done(function(){
						num_active--;
						dfd.notify(++num_done, num_total);
						if (num_done == num_total) dfd.resolve();
						next();
					});
				});
			};
		next();
		return dfd.promise();
	}
}