ajax获取XMLHttpRequest对象的通用方法

var http_request = false;

function createXmlHttpRequest(){http_request = false;if(window.XMLHttpRequest) { //Mozilla 浏览器        http_request = new XMLHttpRequest();        if (http_request.overrideMimeType) {//设置MiME类别            http_request.overrideMimeType("text/xml");        }    }else if (window.ActiveXObject) { // IE浏览器        try {            http_request = new ActiveXObject("Msxml2.XMLHTTP");        } catch (e) {            try {                http_request = new ActiveXObject("Microsoft.XMLHTTP");            } catch (e) {}        }    }}

function XXXXX(){createXmlHttpRequest();if(!http_request){window.alert("不能创建XMLHttpRequest对象实例.");}else{window.alert("创建XMLHttpRequest对象实例成功.");}}