Currently, you can use jQuery.fn.data on plain objects, but the data is stored in a separate cache associated with an expando on the object. For objects, it makes sense for data() to set fields directly on the object and avoid the separate cache. This would make this:

$(obj).data("test", value);

The same as:

obj.test = value;

Except that it would raise the changeData event, opening up some interesting "observable" scenarios such as data linking.

Other uses of data() and data related APIs are interesting, too, and could go a number of different ways. The proposed behavior is:

$(obj).data(); returns obj

$(obj).data({test:value}); same as $.extend(true, obj, {test:value})

$(obj).removeData("test"); same as: delete obj.test

$(obj).removeData(); removes all fields from the object

var obj = { existing: true };

$(obj).data("existing"); // true

Another interesting behavior is with events. This change would cause $(obj).bind(..) to set a field on the object named 'events' with the event handler information (and one called 'handle'). That would be unfortunate when the object is JSON serialized. This problem also exists for uses of data() but is solved by the changes already described. To avoid the 'events' expando from being serialized, this change also modifies how 'events' and 'handle' are stored on plain objects. They are now fields of a 'container' object returned by the 'events' expando. For example:

var fn = $(obj).data("events"), container = fn(), events = container.events, handle = container.handle;

This does somewhat make event handler retrieval more indirect. A few places in event.js had to be changed to call this function if the object is not a dom element, but were done so in an unobtrusive way in the 90% case where it is a dom element.

Also, currently doing "$(obj).data(otherObj)" removes the event handlers for any bound events on the object, since events are stored in the data. They wouldn't be cleared anymore by this operation, since will only 'extend' the wrapped object with the given source object and will leave the 'events' list alone.