Binary Tree in JS : https://www.youtube.com/watch?v=suj1ro8TIVY

bi-tree.js

function serialize(root) {
  if (!root) {
    return 'X,'
  }
  const left = serialize(root.left);
  const right = serialize(root.right);
  return root.val += `,${left}${right}`;
}

function deserialize(str) {
  const nodesLeft = str.split(',');
  return deserializeHelper(nodesLeft);
}
function deserializeHelper(nodesLeft) {
  const val = nodesLeft.shift();
  console.log(val);
  if (val === 'X') return null;
  return {
    val,
    left: deserializeHelper(nodesLeft),
    right: deserializeHelper(nodesLeft),
  };
}

const seed = "1,2,X,X,3,4,X,X,5,X,X,";
const des = deserialize(seed);
console.log(des);
const ser = serialize(des);
console.log('assert', seed === ser);