If another list number is full, how to limit the move to it and trigger function?

[amhoho]

For example, there are three ul, each UL can only have 10 li. If you drag onto the maximum number of regions, it will be fail and trigger function nextpage();

#1:<ul><li></li><li></li><li></li></ul>
#2:<ul><li></li><li></li><li></li>.....10 li....</ul>
#3:<ul><li></li><li></li><li></li></ul>
#1 or #3 cannot drag to #2 .
If #2 has been moving to #1, #1 reached 10, #2 can no longer move to #1

What should I do to achieve this effect? Thank you!

[spidfire]

Translated from https://github.com/johnny/jquery-sortable/issues/213

            isValidTarget: function ($item, container){
                var depth = 1;
                var maxDepth = 2;
                var children = $item.find('ol').first().find('li');
                //Add the amount of parents to the depth
                depth += container.el.parents('ol').length;
                //Increment the depth for each time a child
                while (children.length) {
                    depth++;
                    children = children.find('ol').first().find('li');
                }
                return depth <= maxDepth
            },