JSON string not returning to jquery

I have this following json values being generated dynamically through a web method

[{"AuditoriumName":"XYZ","BookingStartDate":"26-06-2018 00:00:00","BookingEndDate":"26-06-2018 00:00:00","Id":null},{"AuditoriumName":"ABC","BookingStartDate":"27-06-2018 00:00:00","BookingEndDate":"27-06-2018 00:00:00","Id":null}]

but these values are not being passed to JQUERY..

events: function (start, end, callback) {
$.ajax({
type: "POST",
url: "ajaxpg.aspx/TestOnWebService",

success: function (data) {

var events = [];

var obj = $.parseJSON(data.d);              // this is showing error




$(obj.event).each(function () {
events.push({
title: $(this).attr('AuditoriumName'),
start: $(this).attr('BookingStartDate'),
end: $(this).attr('BookingEndDate'),
// id: $(this).attr('id')
});
});
//callback(events);
callback && callback(events);


},
error: function(xhr, status, error) {
alert(xhr.responseText + "iam in error");
}