Function traversal

packages/react-stately/src/data/useTreeData.ts:511–519

(node, {inorder, postorder})

  let i = 0;

  function traversal(node, {inorder, postorder}) {
    inorder?.(node);
    if (node != null) {
      for (let child of node.children ?? []) {
        traversal(child, {inorder, postorder});
        postorder?.(child);
      }
    }
  }

  function inorder(child) {
    // in-order so we add items as we encounter them in the tree, then we can insert them in expected order later