if(node.isExpandable&& node.isExpanded&& node.hasChildren()){// if this is an expanded node, get the first childreturn node.getChildren()[0]; // _TreeNode }else{// find a parent node with a siblingwhile(node && node.isTreeNode){var returnNode = node.getNextSibling();
if(returnNode){return returnNode; // _TreeNode}
node = node.getParent();
}returnnull;
}