IE8 AJAX 不能正常工作 解决办法

function crossDomainAjax(url, successCallback) {

    // IE8 & 9 only Cross domain JSON GET request
    if (‘XDomainRequest‘ in window && window.XDomainRequest !== null) {

        var xdr = new XDomainRequest(); // Use Microsoft XDR
        xdr.open(‘get‘, url);
        xdr.onload = function () {
            var dom = new ActiveXObject(‘Microsoft.XMLDOM‘),
                JSON = $.parseJSON(xdr.responseText);

            dom.async = false;

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

            successCallback(JSON); // internal function
        };

        xdr.onerror = function () {
            _result = false;
        };

        xdr.send();
    }

        // IE7 and lower can‘t do cross domain
    else if (navigator.userAgent.indexOf(‘MSIE‘) != -1 &&
             parseInt(navigator.userAgent.match(/MSIE ([\d.]+)/)[1], 10) < 8) {
        return false;
    }

        // Do normal jQuery AJAX for everything else          
    else {
        $.ajax({
            url: url,
            cache: false,
            dataType: ‘json‘,
            type: ‘GET‘,
            async: false, // must be set to false
            success: function (data, success) {
                successCallback(data);
            }
        });
    }
}

    crossDomainAjax(url, function (data) {
            if ("1" != data) {//data.message
                alert(data);
            } else {
                alert("发送成功!");
                if (isTree == "1") {
                    searchTreedata();
                } else {
                    searchdata();
                }

            }
        });