combobox两级联动

var provinces = [[1,'北京'],[2,'上海']];
var cities = new Array();
cities[1] = [[11,'海淀'],[22,'东城']];
cities[2] = [[33,'黄埔'],[44,'浦东'],[55,'静安']];

var comboProvinces = new Ext.form.ComboBox({
            store: new Ext.data.SimpleStore(  {
                    fields: ["provinceId", "provinceName"],
                    data: provinces
           }),

            listeners:{
                   select:function(combo, record,index){
                          comboCities.clearValue();
                          comboCities.store.loadData(cities[record.data.provinceId]);
                  }
           },

           valueField :"provinceId",
           displayField: "provinceName",
           mode: 'local',
           forceSelection: true,
           blankText:'请选择省份',
           emptyText:'请选择省份',
           hiddenName:'provinceId',
           editable: false,
           triggerAction: 'all',
           allowBlank:true,
           fieldLabel: '请选择省份',
           name: 'provinceId',
           width: 80

});

  var comboCities = new Ext.form.ComboBox({
             store: new Ext.data.SimpleStore(  {
                         fields: ["cityId",'cityName'],
                        data:[]
             }),
             valueField :"cityId",
             displayField: "cityName",
             mode: 'local', 
             forceSelection: true,
             blankText:'选择地区',
             emptyText:'选择地区',
             hiddenName:'cityId',
             editable: false,
             triggerAction: 'all',
             allowBlank:true,
             fieldLabel: '选择地区',
             name: 'cityId',
             width: 80
});
comboProvinces.render(Ext.getBody());
comboCities.render(Ext.getBody());