js+xml生成级联下拉框

需要默认选中时，定义一个变量 var cityId=城市id


下面是js代码
function readxml() {
    var XmlDoc = null;
    if (window.ActiveXObject) {
        XmlDoc = new ActiveXObject("Microsoft.XMLDOM");
        XmlDoc.async = false;
        XmlDoc.load(path + "/web/common/regions.xml");
        browse = "ie";
    } else if (document.implementation
            && document.implementation.createDocument) {
        xmlDoc = document.implementation.createDocument('', '', null);
        xmlDoc.load("regions.xml");
        browse = "ff";
    } else {
        alert('未做与该浏览器的兼容！');
    }

    var root = XmlDoc.documentElement;

    // 获取根节点下面的省节点
    var provinces = root.childNodes;

    var province = document.getElementByIdx_x_x("province");
    var cities = document.getElementByIdx_x_x("regId");
    for ( var i = 0; i < provinces.length; i++) {
        // 获取省节点的name属性的值
        var name = provinces[i].getAttribute("name");
        // 创建一个option
        var opt = document_createElement_x_x("option");
        // 为option添加文本
        opt.a(document_createTextNode(name));
        // 添加到父节点中
        if(cityId!=null&&cityId!=""){
        var citys=provinces[i].childNodes;
        for(var j=0;j<citys.length;j++){
            if(citys[j].getAttribute("id")==cityId){
                opt.selected="selected";
                for ( var j = 0; j < citys.length; j++) {
                    // 创建一个option
                    var opt1 = document_createElement_x_x("option");
                    opt1.value = citys[j].getAttribute("id");
                    // 为option添加文本
                    opt1.a(document_createTextNode(citys[j]
                            .getAttribute("name")));
                    // 添加到父节点中
                    if(citys[j].getAttribute("id")==cityId){
                    opt1.selected="selected";
                    }
                    cities.a(opt1);
                }
            }
        }
        }
        province.a(opt);
    }
    province.onchange = function() {
        var pce = document.getElementByIdx_x_x("province");
        var opts = pce.options;
        var opt1 = opts[pce.selectedIndex];
        var name = opt1.innerText;
        for ( var i = 0; i < provinces.length; i++) {
            // 获取省节点的name属性的值
            var name1 = provinces[i].getAttribute("name");
            if (name == name1) {
                cities.length = 1;// 每次改变的时候清空
                var pros = provinces[i];
                var citys = pros.childNodes;
                for ( var j = 0; j < citys.length; j++) {
                    // 创建一个option
                    var opt1 = document_createElement_x_x("option");
                    opt1.value = citys[j].getAttribute("id");
                    // 为option添加文本
                    opt1.a(document_createTextNode(citys[j]
                            .getAttribute("name")));
                    // 添加到父节点中
                    cities.a(opt1);
                }
            }
        }
    }
}


下面是xml结构
<?xml version="1.0" encoding="utf-8"?>
<regions>
  <province name="湖北">
    <city id="1" name="武汉" isOpen="1" />
    <city id="2" name="黄冈" isOpen="1" />
    <city id="19" name="襄樊" isOpen="1" />
    <city id="22" name="鄂州" isOpen="0" />
    <city id="24" name="黄石" isOpen="1" />
  </province>
  <province name="重庆">
    <city id="23" name="重庆" isOpen="0" />
  </province>
</regions>