IE和FireFox下javascript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 }}