code: function findNested(obj, key, memo) {
    var i, proto = Object.prototype,
        ts = proto.toString;
    ('[object Array]' !== ts.call(memo)) && (memo = []);
    for (i in obj) {
      if (proto.hasOwnProperty.call(obj, i)) {
        if (i === key) {
          memo.push(obj[i]);
        } else if ('[object Array]' === ts.call(obj[i]) || '[object Object]' === ts.call(obj[i])) {
          findNested(obj[i], key, memo);
        }
      }
    }
    return memo;
  }
docs: http://stackoverflow.com/a/15643382/1113977