ajax创建万能的XmlHttpRequest对象

        function CreateXmlHttpRequest() {
            var HttpRequest = null;
            try {
                HttpRequest = new ActiveXObject("Microsoft.XMLHTTP");
            }
            catch (e) {
                try {
                    HttpRequest = new XMLHttpRequest();
                }
                catch (e) {
                    try {
                        HttpRequest = new ActiveXObject("Msxml2.XMLHTTP");
                    }
                    catch (e) {
                        alert("您的浏览器不支持ajax");
                    }
                }
            }
            finally {
                return HttpRequest;
            }
        }

     function CreateXmlHttpRequest() {
            return window.ActiveXObject ? new ActiveXObject("Microsoft.XMLHTTP") : window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject("Msxml2.HTTP");
        }