In-order traverse without recursion

in-order traversal no recursion.js

/**
 * Binary tree in-order traversal.
 *
 * How would look this simple, straightforward algorithm without recursion?
 * I don't like recursion, that's one of my attempts to avoid it.
 */
function traverseInOrderNoRecursion(t) {
  if (!t) {
    return [];
  }

  let waitingNodes = [[t, 0]];
  let visitedNodes = [];
  let values = [];

  while (waitingNodes.length) {
    let [node, depth] = waitingNodes.pop();
    visitedNodes.push([node, depth]);

    if (node.right) {
      waitingNodes.push([node.right, depth + 1]);
    }

    if (node.left) {
      waitingNodes.push([node.left, depth + 1]);
    } else {
      let maxWaitingNodeDepth = waitingNodes.length ? waitingNodes[waitingNodes.length - 1][1] : 0;

      while (visitedNodes.length && visitedNodes[visitedNodes.length - 1][1] >= maxWaitingNodeDepth - 1) {
        values.push(visitedNodes.pop()[0].value);
      }
    }
  }

  return values;
}