javascript 实现 对XML文件 2级/3级联动操作

//实现对xml文档的读取：
function loadXMLDoc(dname) {
    try // Internet Explorer
    {
        xmlDoc = new ActiveXObject("Microsoft.XMLDOM");
    } catch (e) {
        try // Firefox, Mozilla, Opera, etc.
        {
            xmlDoc = document.implementation.createDocument("", "", null);
        } catch (e) {
            alert(e.message)
        }
    }
    try {
        xmlDoc.async = false;
        xmlDoc.load(dname);//加载xml文档
        return (xmlDoc);
    } catch (e) {
        alert(e.message)
    }
    return (null);
}

//实现对xml文档的操作：  
  var stateSelectObj = document.getElementById("state");
            var citySelectObj = document.getElementById("city");
            var regionSelectObj = document.getElementById("region");
            //初始化一个请选择:html dom
            stateSelectObj.add(new Option("--请选择--",""));
            citySelectObj.add(new Option("--请选择--",""));
            regionSelectObj.add(new Option("--请选择--",""));

            //从XML中读取所有的省份，给stateSelect赋值
            var xmlDoc = loadXMLDoc("LocList.xml");//获取到代表XML文件的那个Document对象
            var xmlStateNodes = xmlDoc.getElementsByTagName("State");
            for(var i=0;i<xmlStateNodes.length;i++){
                var xmlStateName = xmlStateNodes[i].getAttribute("Name");
                var xmlStateCode = xmlStateNodes[i].getAttribute("Code");
                stateSelectObj.add(new Option(xmlStateName,xmlStateCode));
            }

            


            //给省份select注册onchange事件
            stateSelectObj.onchange=function(){
                //清空
                citySelectObj.length=0;

                citySelectObj.add(new Option("--请选择--",""));

                if(this.value!=""){
                    for(var i=0;i<xmlStateNodes.length;i++){
                        //在xml中查找所有的State标签，看谁的Code属性和value值一样
                        var xmlStateCode = xmlStateNodes[i].getAttribute("Code");
                        if(this.value==xmlStateCode){
                            //调用该标签的getElementsByTagName,找到子标签。
                            var xmlCityNodes = xmlStateNodes[i].getElementsByTagName("City");
                            for(var j=0;j<xmlCityNodes.length;j++){
                                var xmlCityName = xmlCityNodes[j].getAttribute("Name");
                                var xmlCityCode = xmlCityNodes[j].getAttribute("Code");
                                //添加城市html
                                citySelectObj.add(new Option(xmlCityName,xmlCityCode));
                            }
                            break;
                        }
                    
                    }
                }
            }



            //给市级城市添加onchange事件
            citySelectObj.onchange=function()
            {
                //清空
                regionSelectObj.length=0;
                regionSelectObj.add(new Option("--请选择--",""));

                if(this.value!="")
                {
                    for(var i=0;i<xmlStateNodes.length;i++)
                    {
                        var xmlStateCode = xmlStateNodes[i].getAttribute("Code");
                        if(stateSelectObj.value==xmlStateCode)
                        {
                            var xmlCityNodes = xmlStateNodes[i].getElementsByTagName("City");
                            for(var j=0;j<xmlCityNodes.length;j++)
                            {
                                if(this.value==xmlCityNodes[j].getAttribute("Code"))
                                {
                                    var xmlregionNodes = xmlCityNodes[j].getElementsByTagName("Region");
                                        for(var k=0;k<xmlregionNodes.length;k++)
                                        {
                                            var xmlregionName = xmlregionNodes[k].getAttribute("Name");
                                            var xmlregionCode = xmlregionNodes[k].getAttribute("Code");
                                            //添加城市html
                                            regionSelectObj.add(new Option(xmlregionName,xmlregionCode));
                                        }
                            
                                }
                            }
                        }
                    }
                }
            }