如何在 typescript 中指定枚舉的索引類型

Question

考慮以下示例：

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

}

let index : keyof Color
index = "Green" 

console.log(Color[index])

錯誤

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'.

索引變量必須是枚舉 Color 鍵的字符串版本。 如何指定索引變量的類型？

Answer 1

您應該使用let index: keyof typeof Color ，因為Color實際上是 object （各種字典），因此您需要先使用typeof獲取其類型。 對於keyof和typeof的作用的深入解釋，有一個很好的問題和線程來解釋它。

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

}

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

console.log(Color[index])

請參閱TypeScript Playground上的工作示例。