Update docs for getNextNode and related methods

Author: mbraak

docs/_entries/node/getnextnode.md

@@ -3,12 +3,11 @@ title: getNextNode
 name: node-functions-getnextnode
 ---
 
-Get the next node in the tree.
+Get the next node in the tree. This is the next sibling, if there is one. Or, if there is no next sibling, a node further down in the tree.
 
--   If the node has children, return the first child.
--   If the node is the last child, return the next sibling of the parent.
+This is the next sibling, if there is one. Or, if there is no next sibling, a node further up in the tree.
 
-Returns a node or null.
+-   Returns a node or null.
 
 {% highlight js %}
 var node = node.getNextNode();

docs/_entries/node/getnextvisiblenode.md

@@ -5,7 +5,10 @@ name: node-functions-getnextvisivlenode
 
 Get the next visible node in the tree. Does the same as using the _down_ key.
 
-Returns a node or null.
+This is the previous sibling, if there is one. Or, if there is no previous sibling, a node further up in the tree that is visible.
+
+-   Returns a node or null.
+-   A node is visible if all its parents are open.
 
 {% highlight js %}
 var node = node.getNextVisibleNode();

docs/_entries/node/getpreviousnode.md

@@ -3,9 +3,7 @@ title: getPreviousNode
 name: node-functions-getpreviousnode
 ---
 
-Return the previous node in the tree.
-
-Returns a node or null.
+Return the previous node in the tree. This is the previous sibling, if there is one. Or, if there is no previous sibling, a node further up in the tree.
 
 {% highlight js %}
 var node = node.getPreviousNode();

docs/_entries/node/getpreviousvisiblenode.md

@@ -3,11 +3,12 @@ title: getPreviousVisibleNode
 name: node-functions-getpreviousvisiblenode
 ---
 
--   Get the previous visible node in the tree. Does the same as using the _up_ key.
--   If the previous node is an open parent: return the last child of the node.
--   If the previous node is a closed parent: skip the child nodes of the previous parent, return the previous parent node.
+Get the previous visible node in the tree. Does the same as using the _up_ key.
 
-Returns a node or null.
+This is the previous sibling, if there is one. Or, if there is no previous sibling, a node further up in the tree that is visible.
+
+-   Returns a node or null.
+-   A node is visible if all its parents are open.
 
 {% highlight js %}
 var node = node.getPreviousVisibleNode();