SO

by newblt123

HTML

<select id="one">
    <option value="one">One</option>
    <option value="two">Two</option>
</select>
<select id="two"></select>

JavaScript

function ajaxCall(){
    $.ajax({
        success: function(){
            if($("#one").val() === "one"){
                $("#two").append("<option value='abc'>ABC</option>");
            }
            else{
                $("#two").append("<option value='def'>DEF</option>");
            }
        }
    });
}

$(function(){
    ajaxCall();
    $("#one").change(function(){
        ajaxCall();
    });
});