แปลงต้นไม้จากรูปแบบฐานข้อมูลเป็นรูปแบบ JSON ใน JavaScript

ภาพรวม

สมมติว่าเรามีอาร์เรย์ของอ็อบเจ็กต์จากฐานข้อมูล:

const arr = [
  {"id":7,"name":"Kuwait","parentId":2},
  {"id":4,"name":"Iraq","parentId":2},
  {"id":10,"name":"Qatar","parentId":2},
  {"id":2,"name":"Middle East","parentId":1},
  {"id":3,"name":"Bahrain","parentId":2},
  {"id":6,"name":"Jordan","parentId":2},
  {"id":8,"name":"Lebanon","parentId":2},
  {"id":1,"name":"Africa/Middle East","parentId":null},
  {"id":5,"name":"Israel","parentId":2},
  {"id":9,"name":"Oman","parentId":2}
];

เราต้องเขียนฟังก์ชันแปลงเป็นอาร์เรย์ที่จัดกลุ่มตาม parent

ตัวอย่างโค้ด

const arr = [
  {"id":7,"name":"Kuwait","parentId":2},
  {"id":4,"name":"Iraq","parentId":2},
  {"id":10,"name":"Qatar","parentId":2},
  {"id":2,"name":"Middle East","parentId":1},
  {"id":3,"name":"Bahrain","parentId":2},
  {"id":6,"name":"Jordan","parentId":2},
  {"id":8,"name":"Lebanon","parentId":2},
  {"id":1,"name":"Africa/Middle East","parentId":null},
  {"id":5,"name":"Israel","parentId":2},
  {"id":9,"name":"Oman","parentId":2}
];

const transformTree = (data, root = null) => {
  const res = [];
  const map = {};
  data.forEach((el) => {
    el.children = map[el.id] && map[el.id].children || [];
    map[el.id] = el;
    if (el.parentId === root) {
      res.push(el);
    } else {
      map[el.parentId] = map[el.parentId] || {};
      map[el.parentId].children = map[el.parentId].children || [];
      map[el.parentId].children.push(el);
    }
  });
  return res;
};

console.log(JSON.stringify(transformTree(arr), undefined, 4));

ผลลัพธ์ในคอนโซล

[
  {
    "id": 1,
    "name": "Africa/Middle East",
    "parentId": null,
    "children": [
      {
        "id": 2,
        "name": "Middle East",
        "parentId": 1,
        "children": [
          { "id": 7, "name": "Kuwait", "parentId": 2, "children": [] },
          { "id": 4, "name": "Iraq", "parentId": 2, "children": [] },
          { "id": 10, "name": "Qatar", "parentId": 2, "children": [] },
          { "id": 3, "name": "Bahrain", "parentId": 2, "children": [] },
          { "id": 6, "name": "Jordan", "parentId": 2, "children": [] },
          { "id": 8, "name": "Lebanon", "parentId": 2, "children": [] },
          { "id": 5, "name": "Israel", "parentId": 2, "children": [] },
          { "id": 9, "name": "Oman", "parentId": 2, "children": [] }
        ]
      }
    ]
  }
]