https://www.v2ex.com/t/198927#reply35

gistfile1.js

function tree(id, arr){
  var node = arr.find(a => a.id == id) || { }
  node.items = arr.filter(a => a.pid == id).map(a => tree(a.id, arr))
  return node
}
tree(0, [
    {id:1, pid:0, name:"SYSTEM"},
    {id:2, pid:1, name:"aa"},
    {id:3, pid:2, name:"aaa"},
    {id:4, pid:2, name:"b"},
    {id:5, pid:0, name:"c"},
    {id:6, pid:5, name:"cc"}
])