How to parse json in jquery ajax?

When you are working php or .net etc and you return data like json_encode($data) on ajax request. but in front side you get like a string at that time you have to parse json object and get them. so, let's see example and learn how to use:

Example

var request = $.ajax({
  type: 'POST',
  dataType: 'json',
  url: 'http://www.mysite.com/getpostuser',
  data: {token:obj['token'],postid: obj['postid']}
});
request.done(function(msg) {
  msg = JSON.parse(msg);
  msg.forEach(function(items) {
      var e = "notify-"+items.userid;
      io.sockets.emit(e, 1);
  });
});