How to persist open and closed state of nodes about he-tree HOT 3 CLOSED

let statHandler = (stat) => {
  if (allStates.hasOwnProperty(stat.data.id)) {
    stat.open = allStates[stat.data.id]
    return stat 
  }
}

let allStates = {}
for (const stat of this.$refs.tree.statsFlat) {
  allStates[stat.data.id] = stat.open
}

let statHandler = (stat) => {
  stat.open = allStates[stat.data.id]
  return stat
}