There is an example of queue using rxjs:

Rx.Observable.from(['foo', 'bar', 'baz', 'bay', 'bax', 'bar', 'cat'])
    .do(x => console.log((new Date).toLocaleTimeString() + " " + x))
    // grouping by 2
    .bufferCount(2)
    // concat received results
    .concatMap((data) => {
        return Rx.Observable.defer(() => {
            // assuming long operation here, e.g. downloading,
            // we can use merge here if we want to do operation per item
            return Rx.Observable.create((observer)=>{
                setTimeout(function () {
                    observer.next(data);
                    observer.complete();
                }, 2000);
            })
        });
    })
    .subscribe(
        result => console.log((new Date).toLocaleTimeString() + " finished " + result),
        error => console.error(error),
        () => console.log('done')
    );

// Console ouput
// rxjs.html:9 Console was cleared
// rxjs.html:11 9:56:36 PM foo
// rxjs.html:11 9:56:36 PM bar
// rxjs.html:11 9:56:36 PM baz
// rxjs.html:11 9:56:36 PM bay
// rxjs.html:11 9:56:36 PM bax
// rxjs.html:11 9:56:36 PM bar
// rxjs.html:11 9:56:36 PM cat
// rxjs.html:28 9:56:38 PM finished foo,bar
// rxjs.html:28 9:56:40 PM finished baz,bay
// rxjs.html:28 9:56:42 PM finished bax,bar
// rxjs.html:28 9:56:44 PM finished cat
// rxjs.html:30 done

Used links: