Question

I recently upgraded our project’s jQuery file from 1.4.2 to 1.4.4 and it appears that as of 1.4.3 the way we have been using jQuery.data has stopped working.

We have this code:

var events = $(window).data('events');

if (events.scroll)
if (!events.scroll.include(handler))
  $(window).scroll(handler);

the purpose is to prevent this particular handler from being bound multiple times.

In 1.4.2, this works fine. In 1.4.4, events is undefined.

function handler() {
  //do something
}

$(document).ready(function(){
  $(window).scroll(handler);
  $('div#test').scroll(handler);

  $(window).data('events') -> undefined
  $('div#test').data('events') -> Object
});

What changed with this API? How should I list events for window?

---

I have changed the first line to this:

var events = $(window).data('__events__').events;

a bit messy-looking, but the ability to wire events to plain objects is compelling.

Answer 1

There was a change in jQuery 1.4.3+ for event types, to avoid object name collisions, for window (or any other plain object) use the key "__events__" instead, like this:

var events = $(window).data('__events__');

The same __events__ key is used for any objects that don’t have a .nodeType property (which window doesn’t, so it’s treated like a plain object here).

---

To be clear that this was a conscious, intentional change, it’s included in the jQuery 1.4.3 release notes:

JavaScript Objects
A number of changes were made to when .data() is used on JavaScript objects (or, more accurately, anything that isn’t a DOM node). To start whenever you set data on a JavaScript object the data is set directly on the object – instead of going into the internal data object store. Additionally events that are attached to objects are put in a new __events__ property that is actually a function. This was done to allow events to be attached directly to an object, be garbage collected when the object is collected, and not be serialized by a JSON serializer. These changes should make jQuery’s data and event systems much more useful on JavaScript objects.