封装的Ajax

//============以下是封装的 AJAX
var xmlHttp;

function createXMLHttpRequest() {
    if (window.ActiveXObject) {
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    } else if (window.XMLHttpRequest) {
        xmlHttp = new XMLHttpRequest();
    }
}
   
function startRequest(reqMethod,reqUrl,isSynchronization ,handleStateChange) {
    createXMLHttpRequest();
    xmlHttp.onreadystatechange = handleStateChange;
    xmlHttp.open(reqMethod, reqUrl, isSynchronization);
    xmlHttp.send();
}
   

/** 解析XML字符串
 * @param str 要解析的XML字符串
 * @return document对象
 */
function loadXml(str) {
  if (str == null)
    return null;
  var doc = new ActiveXObject("MSXML.DOMDocument");
  //var doc = new ActiveXObject("Msxml2.DOMDocument.4.0");
  doc.async = false;
  doc.loadXML(str);
  return doc;
}