打字稿：如何检查值是否为有效的Enum键值？

Question

是否有一种方法可以获取打字稿中的枚举名称，例如nameof(FirstEnum)？以下代码在每次定义新的枚举时都必须扩展if开关。有没有更通用的方式可以在打字稿中实现相同的功能？

enum FirstEnum {
    First = 0,
    Second = 1,
    Third = 2,
}
enum SecondEnum {
    One,
    Two,
}


function translateEnum(type$, val): string {
    let lookupKey = '';
    if (type$ === FirstEnum) {
        lookupKey = `firstenum.${FirstEnum[val]}`;
    } else if (type$ === SecondEnum) {
        lookupKey = `secondenum.${SecondEnum[val]}`;
    } else {
        throw new Error('not supported');
    }
    //lookupkey example: secondenum.One
    const result = ''; //translate here, ex. await translationService.translate(lookupkey);
    return result;
}

translateEnum(SecondEnum , SecondEnum.One);

Answer 1

由于将打字稿Enums转换为JavaScript对象，因此您可以使用in运算符检查enum的键值是否是enums的成员。请注意，这仅适用于非enums且基于数字的const。

enum FirstEnum {
    First = 0,
    Second = 1,
    Third = 2,
}
enum SecondEnum {
    One,
    Two,
}


function translateEnum(val: FirstEnum | SecondEnum): string {
    let lookupKey = '';
    if (val in FirstEnum || val in SecondEnum) {
      console.log(`Enum value ${val} is valid!`);
      //lookupkey example: secondenum.One
      const result = ''; //translate here, ex. await translationService.translate(lookupkey);
      return result;
    } else {
        console.log(`Enum value ${val} not supported.`);
        throw new Error('not supported');
    }
}

translateEnum(SecondEnum.One);

translateEnum(10);

输出

Enum value 0 is valid!
Enum value 10 not supported.
Uncaught Error: not supported
    at translateEnum (eval at <anonymous> (main-0.js:804), <anonymous>:23:15)
    at eval (eval at <anonymous> (main-0.js:804), <anonymous>:27:1)
    at main-0.js:804

更多信息

请参阅堆栈溢出问题Check if value exists in enum in TypeScript。