$.ajax({
    type: 'GET',
    url: 'admin.php?import=true',
    success: function (jqxhr) {

        // indexOf() return -1 klau x jumpa substring dlm string
        if(jqxhr.responseText.indexOf('Error :') == -1) {
            location.href = 'admin.php?loading=dismiss?callback=admin.php?upload';
        }
    }
});