TypeScript：如何将 Record 转换为 union

Question

是否可以从这种类型：

type Input = {
    foo: "a" | "b";
    bar: "c" | "d";
};

选择此类型：

type Output = 
    { key: "foo"; value: "a" | "b"; } | 
    { key: "bar"; value: "c" | "d"; };

?
谢谢！

Answer 1

是的，您可以使用映射类型来做到这一点。

type TransformInput<T> = {
  [P in keyof T]: { key: P; value: T[P] }; 
}[keyof T];

type Output = TransformInput<Input>

Output 将计算为

type Output = {
    key: "foo";
    value: "a" | "b";
} | {
    key: "bar";
    value: "c" | "d";
}

TypeScript: How to convert Record to union