convert rx observable to knockout observable with subscription and disposal

gistfile1.txt

(function(){

    function addSubscribeDispose(observable, subscribe, dispose) {
        var subscriptions = [];
        var oldSubscribe = observable.subscribe.bind(observable);
        observable.subscribe = function (callback, callbackTarget, event) {
            var oldDispose, ret;
            ret = oldSubscribe(callback, callbackTarget, event);
            if (!subscriptions.length) {
            	subscribe();
            }
            subscriptions.push(ret);
            oldDispose = ret.dispose;
            ret.dispose = function () {
                subscriptions.splice(subscriptions.indexOf(ret), 1);
                oldDispose.bind(this)();
                
                if (!subscriptions.length) {
                    dispose();
                }
            };
            return ret;
        };
    }
    return function rx2koObservable(initialValue) {
        var observable = ko.observable(initialValue);
        var rxSubscription;
        var _this = this;
        addSubscribeDispose(observable,function(){
        	rxSubscription = _this.subscribe(observable);
        },
		function () {
            return rxSubscription.dispose();
        });
        return observable;
    }
    });