IE和FireFox下学习JavaScript技术读写XML实现广告轮换

最近更新网站首页广告，ASP.NET的广告控件很容易实现这点，可首页是静态页面，联想广告控件的原理决定采用javascript+xml实现这点方面配置，更新广告时只要更新xml即可，方便了广告轮换
xml结构如下
<ad>
<tupian>http://www.seehaha.com/images/060901-150.100.2.gif</tupian>
<tupian>http://www.seehaha.com/xml/061009-300.100.jpg</tupian>
<dizhi>http://www.seehaha.com/plan/</dizhi>
<dizhi>http://www.seehaha.com/va.htm</dizhi>
</ad>
==

// JScript 文件

        var  Now  =  new  Date(); 

         var  Min  =  Now.getSeconds();

        var  i;

        if((Min % 2) == 1)//读取秒数，根据奇偶随机轮换，当然也可以改变此处算法增加xml节点数

  {

  i = 1;

  }

  else  {

  i = 0; 

 }

var url = "xml/ads.xml";

String.prototype.Trim = function() { return this.replace(/(^\s*)|(\s*$)/g, ""); }

var xmlDoc;//判断是否为Firefox或IE

 var moz = (typeof document.implementation != 'undefined')   && (typeof document.implementation.createDocument != 'undefined');

 var ie = (typeof window.ActiveXObject != 'undefined');function importXML(file) { if (moz)  {

   xmlDoc = document.implementation.createDocument("", "doc", null);//创建FIREFOX下XML文档对象 }  else if (ie)  {

   xmlDoc = new ActiveXObject("MSXML2.DOMDocument.3.0");

   xmlDoc.async = false;   while( xmlDoc.readyState != 4) {};//创建IE下XML文档对象 }  xmlDoc.load(file);}importXML(url);//载入xmlfunction updatetupiandizhi(){if (moz) {

var ad = xmlDoc.getElementsByTagName("ad")[0]; var tupian;

    var _tupian = ad.getElementsByTagName("tupian")[i].firstChild.nodeValue;

      if (_tupian)

   tupian = _tupian.Trim();

     //得到tupian,dizhi节点下的值

     var dizhi;

     var _dizhi=ad.getElementsByTagName("dizhi")[i].firstChild.nodeValue;

     if(_dizhi) dizhi = _dizhi.Trim();

      document.getElementById('tupian').href = tupian;

      document.getElementById('dizhi').src = dizhi;   //实现轮换

     } else if (ie) {

var src = xmlDoc.documentElement.selectNodes("tupian");

var href = xmlDoc.documentElement.selectNodes("dizhi");/得到tupian,dizhi节点下的值document.getElementById("dizhi").

href = href(i).text;document.getElementById("tupian").src = src(i).text;   //实现轮换 }}