求助：JavaScript数组reduce统计设备故障次数出错及优化方案

需求说明 #

获取一组包含StationID、Working、Failed、DeviceCreatedDate字段的设备状态数据，需按唯一StationID（对应示例中的user字段）统计各Failed故障类型的出现次数，输出格式参考infoReduced示例。当前编写的reduce统计代码无法正确累加次数，输出不符合预期，现排查问题并提供简洁实现方案。

原始数据示例 #

const rawData = [
  { StationID: "user1", Failed: "ErrorA", Working: true, DeviceCreatedDate: "2024-01-01" },
  { StationID: "user1", Failed: "ErrorB", Working: false, DeviceCreatedDate: "2024-01-02" },
  { StationID: "user1", Failed: "ErrorA", Working: false, DeviceCreatedDate: "2024-01-03" },
  { StationID: "user2", Failed: "ErrorC", Working: false, DeviceCreatedDate: "2024-01-01" },
  { StationID: "user2", Failed: "ErrorA", Working: false, DeviceCreatedDate: "2024-01-02" }
];

期望输出（infoReduced示例） #

const infoReduced = {
  "user1": {
    "ErrorA": 2,
    "ErrorB": 1
  },
  "user2": {
    "ErrorC": 1,
    "ErrorA": 1
  }
};

当前错误代码示例 #

// 常见错误实现：每次覆盖用户的故障统计对象
const wrongResult = rawData.reduce((acc, curr) => {
  const station = curr.StationID;
  const error = curr.Failed;
  // 错误：直接赋值新对象，覆盖原有统计数据
  acc[station] = { [error]: (acc[station]?.[error] || 0) + 1 };
  return acc;
}, {});

当前错误输出 #

{
  "user1": { "ErrorA": 1 },
  "user2": { "ErrorA": 1 }
}

问题原因 #

错误代码中，每次处理数据时都会直接给acc[station]赋值一个新对象，覆盖了该StationID下之前已统计的所有故障类型数据，最终仅保留最后一次处理的故障类型及次数，无法实现累加效果。

简洁优化实现方案 #

方案1：Reduce直接累加（最直观） #

const correctResult = rawData.reduce((acc, { StationID: user, Failed: error }) => {
  // 初始化用户对应的故障统计对象（不存在则创建）
  if (!acc[user]) {
    acc[user] = {};
  }
  // 累加故障次数：存在则+1，不存在则初始化为1
  acc[user][error] = (acc[user][error] || 0) + 1;
  return acc;
}, {});

方案2：ES6扩展运算符简化写法 #

const correctResult = rawData.reduce((acc, curr) => {
  const { StationID: user, Failed: error } = curr;
  // 扩展原有对象，更新对应故障的次数，避免覆盖
  acc[user] = { ...acc[user], [error]: (acc[user]?.[error] || 0) + 1 };
  return acc;
}, {});

方案3：Map结构实现（适合复杂场景扩展） #

const stationMap = new Map();

rawData.forEach(({ StationID: user, Failed: error }) => {
  // 初始化用户的故障统计Map
  if (!stationMap.has(user)) {
    stationMap.set(user, new Map());
  }
  const errorMap = stationMap.get(user);
  // 累加故障次数
  errorMap.set(error, (errorMap.get(error) || 0) + 1);
});

// 转换为目标对象格式
const correctResult = Object.fromEntries(
  Array.from(stationMap.entries()).map(([user, errorMap]) => [
    user,
    Object.fromEntries(errorMap.entries())
  ])
);

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