确保 const（只读）对象的键符合 TypeScript 中的 const（只读）值或类型数组

Question

假设我有一个对象，我想确保它的键符合另一种类型。我正在创建映射键的字典，其中左侧是原始键，右侧是显示的键。我需要在运行时和编译时都可用它，因此将其作为const对象和数组执行似乎有意义吗？

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（是的，我尝试使用元组数组执行此操作，但 TypeScript 现在对我很生气）。

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const allowedKeys = ["cheese_type", "jalapeno_qty", "pepperoni"] as const;\n\nconst keyMap = {\n   cheese_type:  "Cheese type",\n   jalapeno_qty: "Number of jalape\xc3\xb1os",\n   pepperoni: "Pepperoni",\n} as const;\n

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这给了我一个明确映射所有键的类型：

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const keyMap: {\n    readonly cheese_type: "Cheese type";\n    readonly jalapeno_qty: "Number of jalape\xc3\xb1os";\n    readonly pepperoni: "Pepperoni";\n}\n

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（我也可以导出类型）

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export const Keys = typeof allowedKeys\nexport const KeyMap = typeof keyMap\n

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但我也想防止keyMap意外拼写错误或添加不应该有的键，所以我想让它符合数组allowedKeys。

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但如果我这样做，我无法弄清楚如何推断或定义对象值作为只读/常量属性......

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const allowedKeys = ["cheese_type", "jalapeno_qty", "pepperoni"] as const;\ntype Keys = typeof allowedKeys;\n\nconst keyMap: {\n  [key in Keys]: string // oh no\n} = {\n   cheese_type:  "Cheese type",\n   jalapeno_qty: "Number of jalape\xc3\xb1os",\n   pepperoni: "Pepperoni",\n} as const;\n

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有什么方法可以做到这一点，而不会让我陷入疯狂的循环，例如：

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const keyMap: {\n  [key in Keys]: key in keyMap ? keyMap[key] : never; // haha no\n} = {\n   cheese_type:  "Cheese type",\n   jalapeno_qty: "Number of jalape\xc3\xb1os",\n   pepperoni: "Pepperoni",\n} as const;\n

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（最终，我希望能够有两组可以参考的密钥......）

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export type RawKey = typeof keyMap;\nexport type DisplayKey = ValueOf<typeof keyMap>;\n

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Answer 1

您可以使用运算satisfies符来检查值是否与特定类型匹配，而无需将其扩展到该类型，否则会丢弃您想要的信息。

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因此，只要您拥有Keys想要允许的密钥类型：

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const allowedKeys = ["cheese_type", "jalapeno_qty", "pepperoni"] as const;\ntype Keys = typeof allowedKeys[number];\n

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你可以这么说吧keyMap satisfies Record<Keys, string>：

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const keyMap = {\n    cheese_type: "Cheese type",\n    jalapeno_qty: "Number of jalape\xc3\xb1os",\n    pepperoni: "Pepperoni",\n} as const satisfies Record<Keys, string>;\n

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然后keyMap仍然记住其属性的所有文字类型：

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/* const keyMap: {\n    readonly cheese_type: "Cheese type";\n    readonly jalapeno_qty: "Number of jalape\xc3\xb1os";\n    readonly pepperoni: "Pepperoni";\n} */\n

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如果你犯了错误keyMap，编译器应该捕获它们：

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const extraKeyMap = {\n    cheese_type: "Cheese type",\n    jalapeno_qty: "Number of jalape\xc3\xb1os",\n    pepperoni: "Pepperoni",\n    pineapple: "\xe2\x81\x89" // error!\n} as const satisfies Record<Keys, string>;\n\nconst missingKeyMap = {\n    cheese_type: "Cheese type",\n    pepperoni: "Pepperoni",\n} as const satisfies Record<Keys, string>; // error!\n\nconst misspelledKeyMap = {\n    cheese_type: "Cheese type",\n    jalapeno_qty: "Number of jalape\xc3\xb1os",\n    peppperroni: "Preppypony", // error!\n} as const satisfies Record<Keys, string>;\n

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Playground 代码链接

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