I couldn't really find a full documentation for all the check_callback parameters. What I found was:

• http://www.jstree.com/api/#/?f=$.jstree.defaults.core.check_callback
• https://github.com/vakata/jstree#more-on-configuration (mid of the section)

So the signature is function (operation, node, parent, position, more). But that alone leaves many questions open:

• What are all possible situations when the callback gets called and what are the respective values for operation?
• For each situation, what do all the other parameters mean? Especially the more parameter is very complex. I found for dnd it's pos property can vary between i, a and b. What does this mean?

So it would be cool if you could add some more details here.

Thanks!