解决firefox不支持innerText的办法

js代码：
<script>
window.onload = function(){

if(window.navigator.userAgent.toLowerCase().indexOf("msie")==0){ //firefox innerText   
   HTMLElement.prototype.__defineGetter__(     "innerText",  
    function(){  
     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].textContent;  
      else if(childS[i].nodeType==3)  
       anyString += childS[i].nodeValue;  
     }  
     return anyString;  
    }  
   );  
   HTMLElement.prototype.__defineSetter__(     "innerText",  
    function(sText){  
     this.textContent=sText;  
    }  
   );  
};

var test = document.getElementById("test");

var innerText_s = test.innerText;

if( innerText_s == undefined ){

alert( test.textContent ); // firefox

}else{ 

alert( test.innerText);

};





}





</script>

html代码

<div id="test">
      <span style="color:red">test1</span> test2
</div>