Least common ancestor

function pathToX(root, x) {
  if (root === null) {
    return null;
  }
  if (root.value === x) {
    return [x];
  }
  
  let leftPath = pathToX(root.left, x);
  if (leftPath !== null) {
    leftPath.shift(root.value);
    return leftPath;
  }
  
  let rightPath = pathToX(root.right, x);
  if (rightPath !== null) {
    rightPath.shift(root.value);
    return rightPath;
  }
  return null;
}

function LCA(root, j, k) {
  let pathToJ = pathToX(root, j);
  let pathToK = pathToX(root, k);
  
  let LCAToReturn;
  while (pathToJ.length > 0 && pathToK.length > 0) {
    let jNumber = pathToJ.shift();
    let kNumber = pathToK.shift();
    if (jNumber === kNumber) {
      LCAToReturn = kNumber;
    } else {
      break;
    }
  }  
  return LCAToReturn;
}