listToTree，列表转树

const list = [
  {id:1,name:'一级 1',pid:0},
  {id:2,name:'二级 1-1',pid:1},
  {id:3,name:'二级 1-2',pid:1},
  {id:4,name:'三级 1-1-1',pid:2},
  {id:5,name:'一级 2',pid:0},
] 

function listToTree(list){
  return list.filter(e => {
    let pid = e.pid;
    let newArr = list.filter(ele => {
      if(ele.id == pid){
        if(!ele.children){
          ele.children = [];
        }
        ele.children.push(e);
        return true
      }
    });
    return newArr.length===0
  });
}
listToTree(list);