firefox chrome ie9,10,11 不支持selectSingleNode和selectNodes的解决方法

function test(){   
         var perid = document.thisForm.PerID.value;   
           
         var xml="test";   
         if(window.ActiveXObject){      
             var xml=new ActiveXObject("Microsoft.XMLDOM");   
             xml.async=false;   
             xml.load("xxxx.xml");   
               
               
         }else if((typeof document.implementation != 'undefined')&&   
             (typeof document.implementation.createDocument!='undefined')){      
             xml = document.implementation.createDocument("", "", null);   
  
             xml.async=false;   
             xml.load("xxxx.xml");   
  
               
            //firefox并不支持selectSingleNode和selectNodes方法;下面两段是用XPath来解决firefox模拟selectSingleNode和selectNodes方法,正确性有待解决   
             XMLDocument.prototype.selectSingleNode = Element.prototype.selectSingleNode = function (xpath){   
                  var   x = this .selectNodes(xpath)   
                 if ( ! x || x.length < 1 ) return   null ;   
                 return   x[ 0 ];   
             }   
             XMLDocument.prototype.selectNodes = Element.prototype.selectNodes = function (xpath){   
                  var   xpe   =   new   XPathEvaluator();   
                  var   nsResolver   =   xpe.createNSResolver( this .ownerDocument   ==   null    ?   
                     this .documentElement :  this .ownerDocument.documentElement);   
                  var   result   =   xpe.evaluate(xpath,  this , nsResolver,  0 ,  null );   
                  var   found   =   [];   
                  var   res;   
                 while   (res   =   result.iterateNext())   
                     found.push(res);   
                 return   found;   
             }   
               
               
         }     
        //下面就可以用selectSingleNode和selectNodes方法   
         var row=null;   
       
        if(perid.substring(0,5)=="NO" &&　perid.length==9){   
             row=xml.selectSingleNode("root/row[@ID='"+perid+"']");   
            if (row!=null){   
                 document.thisForm.MenuColor.value=row.getAttribute("CssFileName");   
                 ChangeBgColor(document.thisForm.MenuColor.value);   
             }   
         }   
          
     }