GROUP BY in JavaScript-平面数组到嵌套的JSON

我的前端打字文件中有以下列表：

月：

0: {id: 1, companyName: "company14", companyId: 14, flActive: true, purchaseMonth: "2019-12-15T00:00:00", purchaseMonthString: "Dec-2019" , year: 2019, month: "December"}
1: {id: 2, companyName: "company5", companyId: 5, flActive: true, purchaseMonth: "2019-12-15T00:00:00", …}
2: {id: 3, companyName: "company13", companyId: 13, flActive: true, purchaseMonth: "2019-11-15T00:00:00", …}
3: {id: 4, companyName: "company14", companyId: 14, flActive: true, purchaseMonth: "2019-11-15T00:00:00", …}
4: {id: 5, companyName: "company5", companyId: 5, flActive: true, purchaseMonth: "2019-10-15T00:00:00", …}
5: {id: 6, companyName: "company14", companyId: 14, flActive: true, purchaseMonth: "2020-09-15T00:00:00", …}
6: {id: 7, companyName: "company7", companyId: 7, flActive: true, purchaseMonth: "2020-09-15T00:00:00", …}

我希望从中得到一个嵌套的树JSON，按CompnayName和Year属性分组，类似于下面的内容，但采用JSON格式：

我发现了这段代码，但它没有完全返回结果，需要稍微调整一下：

keys = [
    'year',
    'companyName'
  ];

groupBy() {
    const drill = (o, key, ...keys) =>
      key ? drill((o[key] = o[key] || {}), ...keys) : o;
    const result = {};
    for (const e of this.poMonths) {
      const key = drill(
        result,
        e.companyName,
        e.year,

        e.month
      );
    }
    return result;
  }

如何才能使其正常工作？

---

解决方案

您可以使用array.reduce()构建树。它从一个空对象开始，当在特定键下还没有定义对象/数组时(将执行||运算符的右侧)：

数据-lang="js"数据-隐藏="假"数据-控制台="真"数据-巴贝尔="假">

let input = [{id: 1, companyName: "company14", companyId: 14, flActive: true, purchaseMonth: "2019-12-15T00:00:00", year: 2019, month: "December"},
{id: 2, companyName: "company5", companyId: 5, flActive: true, purchaseMonth: "2019-12-15T00:00:00", year: 2019, month: "December"},
{id: 3, companyName: "company13", companyId: 13, flActive: true, purchaseMonth: "2019-11-15T00:00:00", year: 2019, month: "November"},
{id: 4, companyName: "company14", companyId: 14, flActive: true, purchaseMonth: "2019-11-15T00:00:00", year: 2019, month: "December"},
{id: 5, companyName: "company5", companyId: 5, flActive: true, purchaseMonth: "2019-10-15T00:00:00", year: 2019, month: "October"},
{id: 6, companyName: "company14", companyId: 14, flActive: true, purchaseMonth: "2020-09-15T00:00:00", year: 2020, month: "September"},
{id: 7, companyName: "company7", companyId: 7, flActive: true, purchaseMonth: "2020-09-15T00:00:00", year: 2020, month: "September"}]

let months = { "09": "September", "10": "October", "11": "November", "12": "December" }

let result = input.reduce((state,current) => {
   let {companyName, year, month} = current;
   
   let company = state[companyName] || (state[companyName] = {});
   let yearObj = company[year] || (company[year] = {});
   let monthArr = yearObj[month] || (yearObj[month] = []);
   monthArr.push(current);
   
   return state;
}, {});

console.log(result);