vaech

function sort(arr) {
  const obj = Object.fromEntries(arr.map(n => [ n.parent, n ]));
  const sorted = [];

  for (let item = obj['null']; item; item = obj[item.id]) {
    sorted.push(item);
  }

  return sorted;
}

function sort(arr, parent = null) {
  const item = arr.find(n => n.parent === parent);
  return item
    ? [ item, ...sort(arr, item.id) ]
    : [];
}