如何使用JQuery填充级联下拉列表

它应该像

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)    });});