Traverse children from a tree

traverse-tree-children.js

function traverseChildren(node, fn, paths = []) {
  const children = node.children || [];
  let i = 0;
  for (const child of children) {
    const currentPaths = [...paths, i++];
    let stop = fn(child, currentPaths);
    if (!stop) {
      stop = traverseChildren(child, fn, currentPaths);
    }

    if (stop) {
      return true;
    }
  }

  return false;
}

function getNodePathsByIndex(tree, index) {
  let result = [];
  let currentIndex = 0;
  traverseChildren(tree, (node, paths) => {
    if (currentIndex++ === index) {
      result = paths.slice();
      return true;
    }
  });
  return result;
}

const items = {
  name: "root",
  children: [
    {
      name: "child1",
      children: [
        { name: "child1-1" }, { name: "child-2" },
      ],
    },
    {
      name: "child2",
    },
    {
      name: "child3",
      children: [
        { name: "child3-1" }
      ],
    },
  ],
};

console.log("index 0", JSON.stringify(getNodePathsByIndex(items, 0)) === JSON.stringify([0]));
console.log("index 1", JSON.stringify(getNodePathsByIndex(items, 1)) === JSON.stringify([0, 0]));
console.log("index 2", JSON.stringify(getNodePathsByIndex(items, 2)) === JSON.stringify([0, 1]));
console.log("index 3", JSON.stringify(getNodePathsByIndex(items, 3)) === JSON.stringify([1]));
console.log("index 4", JSON.stringify(getNodePathsByIndex(items, 4)) === JSON.stringify([2]));
console.log("index 5", JSON.stringify(getNodePathsByIndex(items, 5)) === JSON.stringify([2, 0]));