99999.js

var cloneGraph = (node) => {
  if (node == null) return node;
  const visited = new Array();

  return cloneHelper(node, visited);
};

const cloneHelper = (node, visited) => {
  const newNode = new Node(node.val);

  visited[node.val] = newNode;

  for (const neighbor of node.neighbors) {
    if (!visited[neighbor.val]) {
      const newNeighbor = cloneHelper(neighbor, visited);
      newNode.neighbors.push(newNeighbor);
    } else {
      const newNeighbor = visited[neighbor.val];
      newNode.neighbors.push(newNeighbor);
    }
  }
  return newNode;
};