<script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<script src="jquery.chained.min.js"></script>

Then lets assume you have the following HTML code:

<select id="mark" name="mark">
  <option value="">--</option>
  <option value="bmw">BMW</option>
  <option value="audi">Audi</option>
</select>
<select id="series" name="series">
  <option value="">--</option>
  <option value="series-3" class="bmw">3 series</option>
  <option value="series-5" class="bmw">5 series</option>
  <option value="series-6" class="bmw">6 series</option>
  <option value="a3" class="audi">A3</option>
  <option value="a4" class="audi">A4</option>
  <option value="a5" class="audi">A5</option>
</select>

You can now chain the #series to #mark. There are two different ways to do it. Choose yourself if you prefer more english like or shorter version. I prefer the shorter version.

$("#series").chained("#mark"); /* or $("#series").chainedTo("#mark"); */

감사합니다.