.attr('class') returns undefined instead of blank

[tryandls]

In previous versions, calling .attr('class') on an element with no class attribute (not one with class="") returned blank. It now returns undefined.

This has the potential to break code, for example something like $('#foo').attr('class').indexOf('bar').

Other than issue #9468, I can't find any mention of this issue. Tested only in FF4.

[tryandls]

Test Case ​http://jsfiddle.net/tryandls/HmUh6/1/

Same results in IE8

[timmywil]

This is due to a fix in attr in 1.6 as that is the intended behavior. It should return the attribute value or undefined if the attribute is not present on the element.