src/chart/tree/layoutHelper.js
function nextRight(node) {
    var children = node.children;
    return children.length && node.isExpand ? children[children.length - 1] : node.hierNode.thread;
}
function nextRight(node) {
    var children = node.children;
    return children.length && node.isExpand ? children[children.length - 1] : node.hierNode.thread;
}
function nextRight ( node ) { var children = node . children ; return children . length && node . isExpand ? children [ children . length - 1 ] : node . hierNode . thread ; }
This function is used to traverse the right contour of a subtree.
It returns the rightmost child of node or the thread of node. The function
returns null if and only if node is on the highest depth of its subtree.

@param  {module:echarts/data/Tree~TreeNode} node
@return {module:echarts/data/Tree~TreeNode}
This function is used to traverse the right contour of a subtree . It returns the rightmost child of node or the thread of node . The function returns null if and only if node is on the highest depth of its subtree .