EasyUI Tree 中的Node state属性

[{"id":1,"text":"Node 1","state":"closed","children":
[{"id":11,"text":"Node 11"},{"id":12,"text":"Node 12"}]},
{"id":2,"text":"Node 2","state":"closed"}]

The node 1 and node 2 are closed, when expand the node 1, it will directly show its child nodes. When expand node 2, it will send the value(2) to server to retrieve child nodes.