Download Youtube video (and subtitles, if video has them)

yt.js

var request = require('request');
var querystring = require('querystring');
var fs = require('fs');
var xml2js = require("xml2js");
var ent = require('ent');
var video_id = 'IgKWPdJWuBQ';
var quality = 'hd720'; // hd1080, hd720, large, highres (original)
Number.prototype.padLeft = function(n,str){
    return Array(n-String(this).length+1).join(str||'0')+this;
}
function seconds2time(seconds) {
  var s = {}
    s.s = parseInt(seconds % 60).padLeft(2).toString() + "." + Number(((seconds % 60) % 1 * 1000).toFixed(3)).padLeft(3).toString();
    s.m = parseInt((seconds / 60) % 60).padLeft(2);
    s.h = parseInt((seconds / 3600) % 24).padLeft(2);
  return [
    s.h, s.m, s.s
  ].join(":");
}
request('http://www.youtube.com/get_video_info?video_id=' + video_id, function(error, response, body){
  var query = querystring.parse(body);
  try {
    if(query.url_encoded_fmt_stream_map){
      var stream = null;
      var stream_map = query.url_encoded_fmt_stream_map.split(',');
      stream_map.forEach(function(senc){
        var s = querystring.parse(senc);
                console.log(s);
        if((/^video\/mp4/).test(s.type) && s.quality === quality){
          stream = s;
        }
      });
      if(stream){
        request(stream.url + '&signature=' + stream.sig).pipe(fs.createWriteStream(video_id + '.mp4'));
        if(query.ttsurl){
          request(query.ttsurl + "&ts=" + new Date().getTime() + "&type=track&lang=en&format=1&kind=&name=", function(err, res, body){
            if(!err && body){
              var subtitles = "";
              var subtitle_row = 1;
              var parser = new xml2js.Parser();
              parser.parseString(body, function(err, result){
                  result.transcript.text.forEach(function(row){
                    var start = seconds2time(parseFloat(row['$'].start));
                    var end = seconds2time(Number((parseFloat(row['$'].start) + parseFloat(row['$'].dur)).toFixed(3)));
                    subtitles += subtitle_row + "\n" + start + " --> " + end + "\n" + ent.decode(row['_']) + "\n\n";
                    subtitle_row++;
                  });
                  fs.writeFileSync(video_id + '.srt', subtitles);
              });
            }
          });
        }
      }
    }
  } catch(err){
    console.log(err);
  }
});