Typescript 如何获取数组所有可能的索引作为数字联合类型

发布于04月25日

如何获得数组的所有可能索引作为数字联合类型？

Expected result a number union type:

type VoiceSettings = {
    similarityLevel: 0 | 1 | 2 | 3 | 4 | 5;
    stabilityLevel: 0 | 1 | 2 | 3 | 4;
}

Actual result:

type VoiceSettings = {
    similarityLevel: "0" | "1" | "2" | "3" | "4";
    stabilityLevel: "0" | "1" | "2" | "3" | "4";
}

Code:

const VALUES_MAP = {
  similarityLevel: [0, 15, 30, 50, 75, 90],
  stabilityLevel: [15, 30, 60, 75, 90],
} as const;

type ValuesTypes = keyof typeof VALUES_MAP;

type VoiceSettings = {
  [key in ValuesTypes]: Exclude<keyof (typeof VALUES_MAP)[ValuesTypes], keyof []>;
};

这是TS playground

推荐答案

在TypScript 4.8及更高版本中，您可以通过在a template literal type中使用an extends constraint on an infer type variable将任意数字字符串literal types转换为对应的数字文字类型.

type StrToNum<T extends string> =
  T extends `${infer N extends number}` ? N : never

type X = StrToNum<"1" | "-7" | "3.14159">;
// type X = 1 | -7 | 3.14159

一旦您这样做，就很容易将其应用于tuple type的数字字符串索引️🤷‍

type VoiceSettings = {
  -readonly [K in keyof ValuesMap]: (
    StrToNum<`${number}` & keyof ValuesMap[K]>
  )
};
/* type VoiceSettings = {
    similarityLevel: 0 | 5 | 1 | 2 | 3 | 4;
    stabilityLevel: 0 | 1 | 2 | 3 | 4;
} */

通过将keyof ValuesMap[K]与`${number}`(占位符模板文本)相交，我们只得到那些类似数字的字符串. 不过，你可以按照你的方式来做，并排除keyof [].

Playground link to code