Update README.md

Author: cheton

README.md

@@ -208,6 +208,35 @@ https://github.com/cheton/infinite-tree/wiki/Functions:-Tree
 
 https://github.com/cheton/infinite-tree/wiki/Functions:-Node
 
+### Node State
+
+Name | Type | Description
+:--- | :--- | :----------
+depth | Number | The depth of a node.
+open | Boolean | Whether the node is expanded.
+path | String | A unique path string representing a node.
+prefixMask | String | The prefix mask.
+total | Number | The total number of child nodes.
+
+#### Flat Tree Structure
+
+https://github.com/cheton/flattree/blob/master/examples/tree1.js
+
+```
+<root>: path=".0", parent="", children=2, total=11, depth=0, prefix="0", open=1, lastChild=1
+Alpha: path=".0.0", parent=".0", children=0, total=0, depth=1, prefix="00", open=0, lastChild=0
+Bravo: path=".0.1", parent=".0", children=3, total=9, depth=1, prefix="00", open=1, lastChild=1
+Charlie: path=".0.1.0", parent=".0.1", children=2, total=4, depth=2, prefix="000", open=1, lastChild=0
+Delta: path=".0.1.0.0", parent=".0.1.0", children=2, total=2, depth=3, prefix="0001", open=1, lastChild=0
+Echo: path=".0.1.0.0.0", parent=".0.1.0.0", children=0, total=0, depth=4, prefix="00011", open=0, lastChild=0
+Foxtrot: path=".0.1.0.0.1", parent=".0.1.0.0", children=0, total=0, depth=4, prefix="00011", open=0, lastChild=1
+Golf: path=".0.1.0.1", parent=".0.1.0", children=0, total=0, depth=3, prefix="0001", open=0, lastChild=1
+Hotel: path=".0.1.1", parent=".0.1", children=1, total=2, depth=2, prefix="000", open=1, lastChild=0
+India: path=".0.1.1.0", parent=".0.1.1", children=1, total=1, depth=3, prefix="0001", open=1, lastChild=1
+Juliet: path=".0.1.1.0.0", parent=".0.1.1.0", children=0, total=0, depth=4, prefix="00010", open=0, lastChild=1
+Kilo: path=".0.1.2", parent=".0.1", children=0, total=0, depth=2, prefix="000", open=0, lastChild=1
+```
+
 ## License
 
 MIT