如何从对象数组中计算指定字段值并生成对应统计新对象

实现代码（JavaScript） #

// 原始数组
const caseList = [
  {
    caseStatus: "Closed",
    caseDays: 5,
    caseRate: 40
  },
  {
    caseStatus: "Closed",
    caseDays: 8,
    caseRate: 25
  },
  {
    caseStatus: "Active",
    caseDays: 5,
    caseRate: undefined
  }
];

// 统计逻辑
const result = caseList.reduce((acc, cur) => {
  if (cur.caseStatus === 'Active') {
    acc.countActive += 1;
  } else if (cur.caseStatus === 'Closed') {
    acc.countClosed += 1;
    acc.ClosedCaseDaysSum += cur.caseDays || 0;
    acc.ClosedCaseRateSum += cur.caseRate || 0;
  }
  return acc;
}, {
  countActive: 0,
  countClosed: 0,
  ClosedCaseDaysSum: 0,
  ClosedCaseRateSum: 0
});

console.log(result);

输出结果 #

运行后得到的result完全符合要求的结构：

{
  countActive: 1,
  countClosed: 2,
  ClosedCaseDaysSum: 13,
  ClosedCaseRateSum: 65
}

补充说明 #

• 用reduce方法单次遍历完成所有统计，时间复杂度为O(n)，效率更高
• 求和时添加|| 0容错处理，即使Closed状态条目出现caseDays/caseRate为undefined、null的异常值，也不会出现NaN的计算错误

内容的提问来源于stack exchange，提问作者creativated