//jQ 1.2.6 amd 1.3.2

jQuery('body').append(jQuery('<ul id="list1">'));
jQuery('body').append(jQuery('<ul id="list2">'));

//creating element with data
var li = jQuery('<li>').text('x').data('foo', 'bar');

console.info(jQuery.data(li[0]));  //-> 2
console.info(jQuery.data(li[0], 'foo'));  //-> bar

//after adding to two elements
jQuery('#list1, #list2').prepend(li);


console.info(jQuery.data(jQuery('#list1 li')[0])); //-> 7 (OK)
console.info(jQuery.data(jQuery('#list1 li')[0], 'foo')); // -> undefined


console.info(jQuery.data(jQuery('#list2 li')[0])); //-> 8 (OK)
console.info(jQuery.data(jQuery('#list2 li')[0], 'foo')); // -> undefined 


//data is missing

jQuery('#list1, #list2').prepend(li);

Since there are two elements in the jQuery object, the prepend is cloning the original li and appending the clone to the second element. The clone does not have the data.

I think the logic behind this is that copying all the

.data

to all elements would be expensive (and remember that

.data

includes all events as well). You still have the option to explicitly copy the data, or better still attach events and data after the implicit cloning occurs.

The docs aren't clear on this, so I'd suggest clearly documenting the behavior to resolve the ticket.

Same issue as #4191, I think. #4284 raises the same issue as an enhancement request.

Whether or not clone (explicit or otherwise) should copy data is a fair question, but it's hard to justify the first element generated by prepend etc getting data and the others not.

In this case you should clone the elements so that you explicitly carry over the data from the old ones (considering that what you describe doesn't carry over events either, this seems like a fair request).

Since #4191 is already fixed this should be as simple as doing .clone(true).