Ajax异步访问数据库，进行判断

<script type="text/javascript">
        var xmlHttp;
        function creatXmlHttp(){
           if(window.XMLHttpRequest){
             xmlHttp = new XMLHttpRequest();
           }else if(window.ActiveXObject){
             xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
           }
        }
       
        function doAjax(){
          var memberUserName =document.getElementById("memberUserName").value;
          creatXmlHttp();
          xmlHttp.open("GET", "<%=path%>/frontwork/MemberUserAction.do?p=memberUserRegValidationActionForward&&otherAccount=" + memberUserName, true);
          xmlHttp.onreadystatechange = dowork;
          xmlHttp.setRequestHeader("If-Modified-Since","0");
          xmlHttp.send(null);
        }
   
       function dowork(){
          if (xmlHttp.readyState == 4) { // 测试状态是否请求完成
      if (xmlHttp.status == 200) { // 如果服务端回应OK
       var text = xmlHttp.responseText;
       var spa = document.getElementById("msg");
       spa.innerHTML = text;//将内容放入
      }
    }
       }
    </script>