如何在打字稿中指定枚举的索引类型

Question

考虑以下示例：

enum Color {
    Green = "green",
    Red = "red"

}

let index : keyof Color
index = "Green" 

console.log(Color[index])

错误

Type '"Green"' is not assignable to type 'number | "toString" | "charAt" | "charCodeAt" | "concat" | "indexOf" | "lastIndexOf" | "localeCompare" | "match" | "replace" | "search" | "slice" | "split" | "substring" | "toLowerCase" | ... 27 more ... | "padEnd"'.
Element implicitly has an 'any' type because expression of type 'number | "toString" | "charAt" | "charCodeAt" | "concat" | "indexOf" | "lastIndexOf" | "localeCompare" | "match" | "replace" | "search" | "slice" | "split" | "substring" | "toLowerCase" | ... 27 more ... | "padEnd"' can't be used to index type 'typeof Color'. No index signature with a parameter of type 'number' was found on type 'typeof Color'.

索引变量必须是枚举颜色键的字符串版本。 如何指定索引变量的类型？

Answer 1

您应该使用 let index: keyof typeof Color，因为 Color 实际上是一个对象（各种字典），因此您需要首先使用 typeof 获取其类型。要深入了解 keyof 和 typeof 的作用，请参阅 an excellent question and thread that explains it。

enum Color {
    Green = "green",
    Red = "red"

}

let index: keyof typeof Color;
index = "Green" 

console.log(Color[index])

参见 TypeScript Playground 上的工作示例。