javascript - How to select option from dropdown and execute onchange Jquery -

i'm doing in worst way i'm trying a) select dropdown option based on received data social networking plugin , b) force onchange event make successive dropmenus appear , populate.

i'm working country, state , city data. upon page load, country dropdown auto populates 2 selections: mexico , united states. when 1 selected, state dropdown auto populates , once state selected city dropdown populates.

here's markup:

<tr> <td id="field-country" class="tags-form"></td>    <td><select onchange="createcountries.getregions(this.value);" name="country_id" id="country_id" value="" style="width: 130px;" class="campos-tabla"></select></td> </tr> <tr>    <td id="field-state" class="tags-form"></td>    <td><select onchange="createcountries.getcities(this.value);" name="state_id" id="state_id" value="" style="width: 130px;" class="campos-tabla"></select></td> </tr> <tr>    <td id="field-city" class="tags-form"></td>    <td><select name='city_id' id="city_id" value=""class="campos-tabla" style="width: 130px;"></select></td> </tr> 

and here's attempt a) select dropdown option based on data received , b) activate onchange event next dropdown menu populate , continue next selection:

_fillfields: function(){  logingygia.fields.firstname.val(logingygia.firstname);  logingygia.fields.lastname.val(logingygia.lastname);  logingygia.fields.email.val(logingygia.email);   if (logingygia.gender == 'm') {     $('#genderm').attr('checked',true);         }         else {             $('#genderf').attr('checked',true);         };  logingygia.fields.birthmonth.val(d2(logingygia.birthmonth));  logingygia.fields.birthday.val(d2(logingygia.birthday));  logingygia.fields.birthyear.val(logingygia.birthyear) if (logingygia.country == 'united states') {         $('#country_id').val(212);             }             else {                 $('#country_id').val(143);             };             if $('#country_id option: selected ').length){                  if ($('#country_id option:selected').length)                     $('#country_id').val("state_id).change();                                 }else{                                   return ("");             };             } }; 

the if (logingygia.country select country correctly. unfortunately, when combine "if country_id: option", no country selected , state dropdown show "selecciona" not populate choices ... makes sense since country not selected.

i'm sure code mess appreciate better minds me.

you're missing parenthese on 1 if, , i'm not sure if can have space after :. also, you're missing quote. , have same if twice.

if ($('#country_id option:selected').length){    $('#country_id').val('state_id').change(); }else{    return (""); }; 

fix syntax , see if fixes it.