How to populate a cascading Dropdown with JQuery

I have created cascading Dropdown for Country, State, City and Zip

It may helpful to someone. Here only some portion of code are posted you can see full working example on jsfiddle.

//Get html elements
var countySel = document.getElementById("countySel");
var stateSel = document.getElementById("stateSel"); 
var citySel = document.getElementById("citySel");
var zipSel = document.getElementById("zipSel");

//Load countries
for (var country in countryStateInfo) {
    countySel.options[countySel.options.length] = new Option(country, country);
}

//County Changed
countySel.onchange = function () {

     stateSel.length = 1; // remove all options bar first
     citySel.length = 1; // remove all options bar first
     zipSel.length = 1; // remove all options bar first

     if (this.selectedIndex < 1)
         return; // done

     for (var state in countryStateInfo[this.value]) {
         stateSel.options[stateSel.options.length] = new Option(state, state);
     }
}

Fiddle Demo

I'm going to provide a second solution, as this post is still up in Google search for 'jquery cascade select'. This is the first select:

<select class="select" id="province" onchange="filterCity();">
  <option value="1">RM</option>
  <option value="2">FI</option>
</select>

and this is the second, disabled until the first is selected:

<select class="select" id="city" disabled>
  <option data-province="RM" value="1">ROMA</option>
  <option data-province="RM" value="2">ANGUILLARA SABAZIA</option>
  <option data-province="FI" value="3">FIRENZE</option>
  <option data-province="FI" value="4">PONTASSIEVE</option>
</select>

this one is not visible, and acts as a container for all the elements filtered out by the selection:

<span id="option-container" style="visibility: hidden; position:absolute;"></span>

Finally, the script that filters:

<script>

    function filterCity(){
      var province = $("#province").find('option:selected').text(); // stores province
      $("#option-container").children().appendTo("#city"); // moves <option> contained in #option-container back to their <select>
      var toMove = $("#city").children("[data-province!='"+province+"']"); // selects city elements to move out
      toMove.appendTo("#option-container"); // moves city elements in #option-container
      $("#city").removeAttr("disabled"); // enables select
};
</script>

It should as simple as

jQuery(function($) {
    var locations = {
        'Germany': ['Duesseldorf', 'Leinfelden-Echterdingen', 'Eschborn'],
        'Spain': ['Barcelona'],
        'Hungary': ['Pecs'],
        'USA': ['Downers Grove'],
        'Mexico': ['Puebla'],
        'South Africa': ['Midrand'],
        'China': ['Beijing'],
        'Russia': ['St. Petersburg'],
    }

    var $locations = $('#location');
    $('#country').change(function () {
        var country = $(this).val(), lcns = locations[country] || [];

        var html = $.map(lcns, function(lcn){
            return '<option value="' + lcn + '">' + lcn + '</option>'
        }).join('');
        $locations.html(html)
    });
});

Demo: Fiddle