Ajax和后台Action类交互封装

在项目中遇到纯js环境，不能用Jquery，因此产生以下纯JS 的Ajax和Action后台进行交互代码，可以写在公共js类中，以供调用。
function getObjXMLReq(){
    var objXMLReq;
    if (window.ActiveXObject && !(navigator.userAgent.indexOf('Mac') >= 0 && navigator.userAgent.indexOf("MSIE") >= 0)){
        objXMLReq = new ActiveXObject("Microsoft.XMLHTTP");
    }
    else if (window.XMLHttpRequest){
        objXMLReq = new XMLHttpRequest();
    }
    return objXMLReq;
}

function proxyRequest(action, method, parameter,isAsynchronism) {
    var objXMLReq = getObjXMLReq();
    var strURL =   action + ".do";
    var flag = false;
    if(method != null && method != ""){
        strURL += "?method=" + method;
        flag = true;
    }
    if (parameter == null) parameter = "";
   
    if(flag)
    strURL += "&isPartlyRefresh=true"+parameter;
    else
      strURL += "?isPartlyRefresh=true"+parameter;

    if(!isAsynchronism) isAsynchronism = false;
    objXMLReq.open("POST", strURL, isAsynchronism);
    objXMLReq.send(parameter);
      var strResult = objXMLReq.responseText;
     
      return strResult;
    }