(ES6)數據處理常用工具方法收集(更新狀態: on)

1. 扁平數組轉成tree結構(來源: StackOverflow的印度老哥寫的)

 1 // Data Set
 2 // One top level comment 
 3 var comments = [{
 4     id: 1,
 5     parent_id: null
 6 }, {
 7     id: 2,
 8     parent_id: 1
 9 }, {
10     id: 3,
11     parent_id: 1
12 }, {
13     id: 4,
14     parent_id: 2
15 }, {
16     id: 5,
17     parent_id: 4
18 }];
19 
20 const nest = (items, id = null, link = 'parent_id') =>
21   items
22     .filter(item => item[link] === id)
23     .map(item => ({ ...item, children: nest(items, item.id) }));
24 
25 nest(comments);