javascript html页面中的内容替换

<script language="javascript">

function ffRed(){
 var xsxf = document.getElementById("id");
 var str2 = "字段1";
 var str3 = "字段2";
 var reg=eval("/"+str2+"/gi");
 var reg3=eval("/"+str3+"/gi");
 xsxf.innerHTML =  xsxf.innerHTML.replace(reg,"<font color='#FF0000'>字段1</font>");
 xsxf.innerHTML =  xsxf.innerHTML.replace(reg3,"<font color='#FF0000'>字段2</font>");
}
ffRed();

</script>