ajax_创建

<script>
 function createAjax(){
  var request=false;

  //window对象中有XMLHttpRequest存在就是非IE,包括(ie7,8)
  if(window.XMLHttpRequest){
   request=new XMLHttpRequest();

   if(request.overrideMineType){
    request.overrideMineType("text/xml");
   }
  //windows对象中有ActiveXobject属性存在就是IE
  }else if(window.ActiveXObject){
  var versions=['Microsoft.XMLHTTP','MSXML.XMLHTTP','Msxml2.XMLHTTP.7.0','Msxml2.XMLHTTP.6.0','Msxml2.XMLHTTP.5.0','Msxml2.XMLHTTP.4.0','MSXML2.XMLHTTP.3.0','MSXML2.XMLHTTP'];
  for (var i=0;i<versions.length;i++)
  try{
   request=new ActiveXObject();
   if(request){
    return request;
   }
   }catch(e){
   request=false;
 }
    }
  return request;
 }
 var ajax=createAjax();
 alert(ajax);
</script>