function convert(str) {
  var date = new Date(str),
    mnth = ("0" + (date.getMonth() + 1)).slice(-2),
    day = ("0" + date.getDate()).slice(-2);
  return [date.getFullYear(), mnth, day].join("-");
}

console.log(convert("Thu Jun 09 2011 00:00:00 GMT+0530 (India Standard Time)"))
//-> "2011-06-08"