Ajax: asynchronous javascript and xml (异步javascript和xml) 主流浏览器方式创建 var xhr = new XMLHttpRequest(); IE(6/7/8)方式 var xhr = new ActiveXObject(“Microsoft.XMLHTTP”); //最原始方式 var xhr = new ActiveXObject(“Msxml2.XMLHTTP”); //升级 var xhr = new ActiveXObject(“Msxml2.XMLHTTP.3.0”); //升级 var xhr = new ActiveXObject(“Msxml2.XMLHTTP.5.0”); //升级 var xhr = new ActiveXObject(“Msxml2.XMLHTTP.6.0”); //IE维护的最高版本