var xhrFactory = function () {
    this.init.apply(this, arguments);
   }
   xhrFactory.prototype = {
    init: function () {
     this.xhr = this.create();
    },
    create: function () {
     var xhr = null;
     try {
      if (window.XMLHttpRequest) {
       xhr = new XMLHttpRequest();
      }
      else if (window.ActiveXObject) {
       xhr = new ActiveXObject("Msxml2.Xmlhttp");
      }
     }
     catch (err) {
      xhr = new ActiveXObject("Microsoft.Xmlhttp");
     }
     return xhr;
    }
}

readystate: function (timeout,callback) {
     this.xhr.onreadystatechange = function () {
      if (this.readyState == 4 && this.status == 200) {
       callback(eval("(" + this.responseText + ")"));
      }
      else {
       setTimeout(function () {
        this.xhr.abort();
       }, !timeout ? 15000 : timeout);
      }
      
     }
    }

para: function (data) {
     var datastr = "";
     if (data && Object.prototype.toString.call(data) == "[object Object]") {
      for (var i in data) {
       for (var i = 0; i < length; i++) {
        datastr += i + "=" + data[i] + "&";
       }
      }
     }
     return datastr;
    }

get: function (url, data, callback, async, timeout) {
     this.readystate(timeout, callback);
     var newurl = url;
     var datastr = this.para(data);
     newurl = url + "?" + datastr;
     this.xhr.open("get", newurl, !async ? true : async);
     this.xhr.send(null);
    }

post: function (url, data, callback, async, timeout) {
     this.readystate(timeout, callback);
     var newurl = url;
     var datastr = this.para(data);
     this.xhr.open("post", newurl, !async ? true : async);
     this.xhr.setRequestHeader("content-type", "x-www-form-urlencoded");
     this.xhr.send(!datastr ? null : datastr);
    }

var xhr = new xhrFactory();
   xhr.post("test.ashx", null, function (data) {
    alert(data);
   });