javascript - js writes a recursion to restructure the data structure into another structure

Question

Now we have the following data structure:

[{
    id: 1,
    pid: 0,
    name: "年级"
}, {
    id: 2,
    pid: 1,
    name: "一年级"
}, {
    id: 3,
    pid: 1,
    name: "二年级"
}, {
    id: 4,
    pid: 0,
    name: "专业"
}, {
    id: 5,
    pid: 4,
    name: "单片机开发"
}]

Write a JS method to convert it into the following format data:

[{
    id: 1,
    pid: 0,
    name: "年级",
    children: [{
        id: 2,
        pid: 1,
        name: "一年级"
    }, {
        id: 3,
        pid: 1,
        name: "二年级"
    }]
}, {
    id: 4,
    pid: 0,
    name: "专业",
    children: [{
        id: 5,
        pid: 4,
        name: "单片机开发"
    }]
}]

Answer 1

var list = [{
    id: 1,
    pid: 0,
    name: "年级"
}, {
    id: 2,
    pid: 1,
    name: "一年级"
}, {
    id: 3,
    pid: 1,
    name: "二年级"
}, {
    id: 4,
    pid: 0,
    name: "专业"
}, {
    id: 5,
    pid: 4,
    name: "单片机开发"
}];

function parseList (list) {
    var map = {};
    list.forEach(function (item) {
        if (!map[item.id]) {
            map[item.id] = item; 
        }
    });
    list.forEach(function (item) {
        if (item.pid != 0) {
            map[item.pid].chidren ? map[item.pid].chidren.push(item) : map[item.pid].chidren = [item];
        }
    });

    return list.filter(function (item) {
        return item.pid === 0;
    });
}

var newList = parseList(list);

Answer 2

var list = [
    { id: 1, pid: 0, name: "年级" },
    { id: 2, pid: 1, name: "一年级" },
    { id: 3, pid: 1, name: "二年级" },
    { id: 4, pid: 0, name: "专业" },
    { id: 5, pid: 4, name: "单片机开发" }
];

// 生成查找表，可以按 id 查到节点
const dict = list.reduce((all, item) => {
    all[item.id] = item;
    return all;
}, {});

// 由于原始数据没有 id 为 0 的根节点，
// 这里模拟一个，最终它的 children 就是实际的所有根节点
var root = {
    id: 0
};
dict[0] = root;

// 循环添加关系
list.forEach(item => {
    const parent = dict[item.pid];
    // 确保父节点的 children 存在
    parent.children = parent.children || [];
    parent.children.push(item);
});

// 输出结果 root.children
// 注意，root 不是结果，root.children 才是
console.log(JSON.stringify(root.children, null, 4));

Answer 3

Please refer to it

var sortedData = data.reduce((result, item) => {
  result[item.id] = Object.assign({}, item)
  return result
}, [])

var result = sortedData.reduce((result, item) => {
  if (item.pid === 0) {
    result.push(item)
  } else {
    if (sortedData[item.pid].children) {
      sortedData[item.pid].children.push(item)
    } else {
      sortedData[item.pid].children = [item]
    }
  }
  return result
}, [])