面试一脸懵：listToTree

const tree = [
  {id: -1,parentId: null},
  {id: 0,parentId: -1},
  {id: 1,parentId: -1},
  {id: 2,parentId: -1},
  {id: 3, parentId: 2},
  {id: 4, parentId: 3},
]
转化为
[{"id":-1,"children":[{"id":0},{"id":1},{"id":2,"children":[{"id":3,"children":[{"id":4}]}]}]}]
function listToTree(list){
  let map = new Map()
  list.forEach(item=>{
    if(!map.has(item.parentId)){
      map.set(item.parentId, [])
    }
    map.get(item.parentId).push(item)
  })  
  function rev(root){
    return map.get(root).map(item=>{
      if(map.has(item.id)){
        item.children = rev(item.id)
      }
      delete item.parentId
      return item
    })
  }
  return rev(null)
}