JS火狐与IE的差别

function isIE(){ //ie? 
       if (window.navigator.userAgent.toLowerCase().indexOf("msie")>=1) 
          return true; 
       else 
          return false; 
    } 

    if(!isIE()){ //firefox innerText define
        HTMLElement.prototype.__defineGetter__("innerText", function(){
            var textRange = this.ownerDocument.createRange();  
            textRange.selectNodeContents(this);  
            return textRange.toString();  
            
            var anyString = "";
            var childS = this.childNodes;
            for(var i=0; i<childS.length; i++){
               if(childS[i].nodeType==1)
                 anyString += childS[i].tagName=="BR" ? '\n' : childS[i].innerText;
               else if(childS[i].nodeType==3)
                 anyString += childS[i].nodeValue;
            }
             return anyString;
       }); 
       HTMLElement.prototype.__defineSetter__("innerText",function(sText){ 
          this.textContent=sText; 
       }); 
    }