How to add node to TreeView control using Javascript

I just want to know how to add a node control to a TreeView (which takes its data from a database with a parent-child relationship). Of course, when I select a node, the new node I want to add should be added under the selected one, and after adding it to the selected node, I want to add the new node to the database too. I can handle the database part, but I don't know how to make the client part.

Hopefully I could describe the problem.

Thanks in advance....