Gives you the ability to create or override methods returning deferred objects so that only one request can be fired at a time.

semaphore.js

// examples:
// create a new function : customRequest = Semaphore.request($.ajax);
// override a function: Backbone.sync = Semaphore.request(Backbone.sync);
Semaphore = function() {
	// private attributes
	var available = true;

	// private api
	function lock() {
		available = false;
	}

	function unlock() {
		available = true;
	}

	function getLock() {
		var temp = available;

		if (available) {
			lock();
		}

		return temp;
	}

	// public api
	var publicApi = {

		// semaphored-request constructor
		request: function(proto) {
			return function() {
				if (getLock()) {
					var deferred = proto.apply(this, arguments);

					deferred.complete(function() {
						unlock();
					});
				}
				else {
					var deferred = null;
				}

				return deferred;
			};
		},
		available: function() {
			return available;
		}
	}

	return publicApi;
};