While testing jQuery 1.8 RC1, I encountered inconsistent behavior between $.data and $().data when reading inline data attributes.

When $.data is used first, the return value is always undefined. Once $().data is used with the same element, then $.data will work.

jsFiddle: http://jsfiddle.net/t76Kc/6/

The specific use case I encountered this was inside a $().each function, trying to add specific data to each individual element. Since .each provides the element, I was trying to avoid an extra $() wrapper around the element if I did not need it.

I think this bug also existed in previous versions of jQuery.