How to read injected Data from DOM-Object?

How to read injected Data from DOM-Object?

Hi,

I store data to an DOM objekt in JavaScript like this:
  1. td["dayDate"] = day_date;

Now, every cell in my generated calendar have it´s right Date in it´s DOM-Inspector:













Now i´m using a jQuery plugin: http://medialize.github.io/jQuery-contextMenu/demo.html

If i start a callback over this plugin on a clicked cell-object with:

  1. console.log($(this));

...i get the right object. Example:


And when i click on that in the console, then the DOM-inspector shows me the right objects inclusive my stored daydate-data.

If i want to get the data in this callback-function like this:

  1. console.log($(this).data("dayDate"));

...i get an "undefined" !!!!!


Why??? What went wrong?
How can i get the data?