Scraping html using [jsdom + qs]

I'm new to using jsdom and querystring. I'm trying to scrape a page for all of the soundcloud track_id's within all of the iframe html tags. The code below logs undefined because the first iframe is not a soundcloud player.

How do I...

1. Modify the code to retrieve all of the iframe instances

2. Check if http://w.soundcloud.com/player/?url=http%3A%2F%2Fapi.soundcloud.com%2Ftracks%2F or just soundcloud is present using jsdom/qs. (I can use an if string contains string type of js test, but I figure there is a better way using jsdom/qs).

   jsdom.env({
    html: 'A_URL',
    scripts: [
      'http://code.jquery.com/jquery-1.5.min.js'
    ],
    done: function(errors, window) {
     var $ = window.$;
     var src = $('iframe').attr('src');
     var aRes = qs.parse(decodeURIComponent(url.parse(src).query)).url.split('/');
     var track_id = aRes[aRes.length-1];
   
    console.log("track_id =", track_id);
    }
   });