在javascript中对对象数组中的相似键求和

Question

我有一个对象数组，如下所示：-

0: {Id: 0, count1: 5, count2: 10, yearMonth: "201803"}
1: {Id: 0, count1: 10, count2: 0, yearMonth: "201804"}
2: {Id: 1, count1: 900, count2: 200, yearMonth: "201805"}
3: {Id: 0, count1: 10, count2: 0, yearMonth: "201806"}
4: {Id: 1, count1: 100, count2: 100, yearMonth: "201807"}
5: {Id: 1, count1: 100, count2: 2, yearMonth: "201808"}

我想将相似的键相加得到 预期输出：

1: {Id: 0, count1: 25, count2: 10}
2: {Id: 1, count1: 1100, count2: 402}

是否可以使用任何数学运算或reduce或任何其他javascript方法来实现？

谢谢

Answer 1

您可以通过使用哈希表和键数组来对所需值求和来减少数组。

var data = [{ Id: 0, count1: 5, count2: 10, yearMonth: "201803" }, { Id: 0, count1: 10, count2: 0, yearMonth: "201804" }, { Id: 1, count1: 900, count2: 200, yearMonth: "201805" }, { Id: 0, count1: 10, count2: 0, yearMonth: "201806" }, { Id: 1, count1: 100, count2: 100, yearMonth: "201807" }, { Id: 1, count1: 100, count2: 2, yearMonth: "201808" }],
    keys = ['count1', 'count2'],
    grouped = Object.values(data.reduce((result, object) => {
        result[object.Id] = result[object.Id] || { Id: object.Id };
        keys.forEach(key => result[object.Id][key] = (result[object.Id][key] || 0) + object[key]);
        return result;
    }, Object.create(null)));

console.log(grouped);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 2

通过淘汰赛，您可以使用一系列计算属性来获得所需的（UI？）格式！

_{免责声明：我假设此列表不会包含数千个项目}

1。分组

第一步是从项目列表 (ko.observableArray([])) 转到按 id 分组的计算对象：

// Search for "group by javascript" to have this function explained
const groupBy = (prop, xs) => xs.reduce(
  (acc, x) => Object.assign(acc, { [x[prop]]: (acc[x[prop]] || []).concat(x) }), {}
);

const items = ko.observableArray([]);

const itemsById = ko.pureComputed(() =>
  groupBy("Id", items())
);

itemsById.subscribe(console.log);
items([{Id: 0, count1: 5, count2: 10, yearMonth: "201803"},{Id: 0, count1: 10, count2: 0, yearMonth: "201804"},{Id: 1, count1: 900, count2: 200, yearMonth: "201805"},{Id: 0, count1: 10, count2: 0, yearMonth: "201806"},{Id: 1, count1: 100, count2: 100, yearMonth: "201807"},{Id: 1, count1: 100, count2: 2, yearMonth: "201808"}]);

<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.2/knockout-min.js"></script>

2。合并

现在我们已经对需要汇总的项目列表进行了分组，我们可以开始应用我们的合并逻辑：

const itemsWithSameId = [{Id:0,count1:5,count2:10,yearMonth:"201803"},{Id:0,count1:10,count2:0,yearMonth:"201804"},{Id:0,count1:10,count2:0,yearMonth:"201806"}];

const merge = (itemA, itemB) => ({
  Id: itemB.Id,
  count1: itemA.count1 + itemB.count1,
  count2: itemA.count2 + itemB.count2
});

// Look up "merging objects using reduce in javascript" to find out more
console.log(
  itemsWithSameId.reduce(merge, { count1: 0, count2: 0 })
)

3。从索引对象返回到数组

现在我们知道如何合并我们的组，我们可以在 UI 中回到我们需要的数组：

// Utilities:
const groupBy = (prop, xs) => xs.reduce(
  (acc, x) => Object.assign(acc, {
    [x[prop]]: (acc[x[prop]] || []).concat(x)
  }), {}
);

// Data Logic:
const merge = (itemA, itemB) => ({
  Id: itemB.Id,
  count1: itemA.count1 + itemB.count1,
  count2: itemA.count2 + itemB.count2
});

// App
const items = ko.observableArray([]);
const itemsById = ko.pureComputed(() =>
  groupBy("Id", items())
);

// Look up "mapping over the values of a javascript object" for more info
const summedItems = ko.pureComputed(() =>
  Object
    .values(itemsById())
    .map(items => items.reduce(merge, { count1: 0, count2: 0 }))
);

// Apply bindings with viewmodel exposing summedItems
ko.applyBindings({ summedItems });

// Inject data (probably in success callback of ajax call)
items([{Id: 0, count1: 5, count2: 10, yearMonth: "201803"},{Id: 0, count1: 10, count2: 0, yearMonth: "201804"},{Id: 1, count1: 900, count2: 200, yearMonth: "201805"},{Id: 0, count1: 10, count2: 0, yearMonth: "201806"},{Id: 1, count1: 100, count2: 100, yearMonth: "201807"},{Id: 1, count1: 100, count2: 2, yearMonth: "201808"}]);

<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.2/knockout-min.js"></script>

<table>
  <thead>
    <tr>
      <th>Id</th>
      <th>Count 1</th>
      <th>Count 2</th>
    </tr>
  </thead>
  <tbody data-bind="foreach: summedItems">
    <td data-bind="text: Id"></td>
    <td data-bind="text: count1"></td>
    <td data-bind="text: count2"></td>
  </tbody>
</table>