I wrote this to standardize all the meta data that i wanted in my documents:

    function Shlock(kind, method, url, data) {
      this.kind = kind;
      this.method = method;
      this.url = url;
      this.data = data;
      this.time = new Date().toJSON();
    };

Then I used it like this:

vis.on("mousedown", function() {
  var self  = this;
  var point = mousePoint(self);
  var pack = {};
  pack.point = point;
  pack.client = gClient;

  var ev = new Shlock('web','point','/force-hcp1.html',pack);

  socket.emit('point',{'shlock':ev});
  restart();
});


But, pack is an object that has elements which are objects themselves.
And that makes filtering via Mongo's built in field filtering API not work.