01.<select id=main >
02.<option value="sec1">Sec 1</option>
03.<option value="sec2">Sec 2</option>
04.</select>
05.
06.<select id=child >
07.<option value="s1-1" section="sec 1" >Sec1 value 1</option>
08.<option value="s1-2" section="sec 1" >Sec1 value 2</option>
09.<option value="s2-1" section="sec 2" >Sec2 value 1</option>
10.<option value="s2-2" section="sec 2" >Sec2 value 2</option>
11.</select>
12.<script>
13.$(document).ready(()=>{
14. $('#main').change(function(){
15. let sec = $(this).val();
16. $('#child option').hide();
17. $('#child option[section="${sec}"]`).show();
18. });
19.});
20.</script>
