[Rails] Suggestion for Ajax-Framework, for RoR

Hello,
I have build a table called Project, in RoR with Nested Sets (this means
the table has a parent_id, lft and rgt).
This table has now several records of projects, that I have inserted via
the console, and with the methods provided by the plugin
acts_as_netsed_set.
What I wanna do now is, to create a treeview of the project table with a
JavaScript Library. I've looked at ExtJS, but I think this is too heavy
for my requirements.
I just need to create a tree and to every item in the tree, I need 4
links (maybe through columns, so that every link is in another column),
because every item should point to 4 different pages with details of the
project.
Does anyone know a good Ajax-Framework that is small and supports things
like this?
Thank you very much.
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