IE 7 Ajax调用破解

Question

fiddler中的ajax调用正在发生并返回带有json响应的200 OK但是onload函数错误输出并且显示的错误是“对象不支持此属性或方法”xdr.onload

    if($.browser.msie) {

      if(window.XDomainRequest == undefined) {
        var xdr = new ActiveXObject('Microsoft.XMLHTTP');
      } else {
        var xdr = new XDomainRequest();  
      }

      xdr.open("post", ajaxStatusUrl+"?buster="+ new Date().getTime());

      setTimeout(function() {
        xdr.send();
      }, 1000);

      xdr.onload = function() {
        var JSON = $.parseJSON(xdr.responseText);

        if(JSON == null || typeof (JSON) == 'undefined') {
          JSON = $.parseJSON(data.firstChild,textContent);
        }
        processData(JSON);
      };

      xdr.onprogress = function() {};
      xdr.ontimeout = function() {};
      xdr.onerror = function() {
        alert('error');
      };

    } else {

        $.ajax({
          type: "POST",
          url: ajaxStatusUrl+"?buster="+ new Date().getTime(),
          processData: true,
          dataType: "json",
          success: function(data) {
            processData(data);
          }
        });
      }
  });