如何将TypeScript枚举转换为同键的另一个枚举？

我有两个结构相似的TypeScript枚举，需要实现它们之间的双向转换。枚举定义如下：

export enum WeekDay {
    MONDAY = "MONDAY",
    TUESDAY = "TUESDAY",
    WEDNESDAY = "WEDNESDAY",
    THURSDAY = "THURSDAY",
    FRIDAY = "FRIDAY",
    SATURDAY = "SATURDAY",
    SUNDAY = "SUNDAY"
}

export enum SpecialWeekDay {
    MONDAY = "Moon's Day",
    TUESDAY = "Tyr's Day",
    WEDNESDAY = "Odin's Day",
    THURSDAY = "Thor's Day",
    FRIDAY = "Freya's Day",
    SATURDAY = "Saturn's Day",
    SUNDAY = "Sun's Day"
}

我之前尝试用以下代码转换，但无效，问题出在代码是通过值而非键来匹配：

let value: SpecialWeekDay = SpecialWeekDay.MONDAY;
let newValue: WeekDay = WeekDay[SpecialWeekDay[value] as keyof typeof WeekDay];

我需要一种无需手动创建映射的简单实现，且支持双向转换。

解决方案 #

由于两个枚举的键完全一致，可以基于枚举键来实现通用转换，无需依赖值的匹配。

通用转换函数

function convertEnum<T extends Record<string, string>, U extends Record<string, string>>(
  value: T[keyof T],
  fromEnum: T,
  toEnum: U
): U[keyof U] {
  // 根据枚举值找到对应的键
  const key = Object.keys(fromEnum).find(k => fromEnum[k] === value) as keyof T;
  // 返回目标枚举对应键的值
  return toEnum[key];
}

双向转换示例

1. SpecialWeekDay → WeekDay

const specialDay: SpecialWeekDay = SpecialWeekDay.MONDAY;
const normalDay: WeekDay = convertEnum(specialDay, SpecialWeekDay, WeekDay);
// normalDay 结果为 WeekDay.MONDAY

2. WeekDay → SpecialWeekDay

const normalDay: WeekDay = WeekDay.FRIDAY;
const specialDay: SpecialWeekDay = convertEnum(normalDay, WeekDay, SpecialWeekDay);
// specialDay 结果为 SpecialWeekDay.FRIDAY

原代码失效原因

字符串枚举不会自动生成反向映射，SpecialWeekDay[value]中value是枚举值（比如"Moon's Day"），枚举对象里没有这个键，因此无法获取到对应的枚举键，导致转换失败。而基于键的转换逻辑利用了两个枚举键完全一致的特性，能稳定完成转换。

内容的提问来源于stack exchange，提问作者Jamie P