Question

I want to create a select tag for countries that when we select the country it hides all optgroups and their contents of a select tag for states except the optgroup and its content which has the same label as the selected country option, example

<select name="country">
<option value="United States">United States</option>     <!-- if I select US -->
<option value="Canada">Canada</option>
<option value="Mexico">Mexico</option>
</select>

<select name="country">
<optgroup label="United States">
<option value="California">California</option>           <!-- Only these states -->
<option value="New York">New York</option>               <!-- are displayed -->
</optgroup>
<optgroup label="Canada">                                <!-- hidden-->
<option value="Ontario">Ontario</option>                 <!-- hidden-->
<option value="Quebec">Quebec</option>                   <!-- hidden-->
</optgroup>
<optgroup label="Mexico">                                <!-- hidden-->
<option value="Baja California">Baja California</option> <!-- hidden-->
<option value="Mexico Estado">Mexico Estado</option>     <!-- hidden-->
</optgroup>
</select>

Answer 1

This seems to be working fine for me:

​$("select[name='country']:eq(0)"​).on("change", function() {
    $("select[name='country']:eq(1)")
        .find("optgroup,option")
        .hide()
        .filter("[label='" + this.value + "'],[label='" + this.value + "'] > *")
        .show();
});​​​​​​​​

DEMO: http://jsfiddle.net/MVkXg/