How to wrap (to group) a list of elements into another element with jquery?

Question

I have the following structure.

Answer 1

You can do it with wrapAll:

var a = $('li');
do $(a.slice(0,3)).wrapAll('
');   
while((a = a.slice(3)).length>0)

example: http://jsfiddle.net/niklasvh/mZr4h/