typescript - 如何获得 TypeScript 映射类型的逆？

Question

我正在寻找 TypeScript 映射类型的“逆”(其属性严格是字符串，以便“可逆”)。为了说明我想要的结果，我需要一个通用的 type

type Inverse<M> = ...

能够转换

type MappedType = {
  key1: 'value1'
  key2: 'value2'
};

进入

/**
 * {
 *   value1: 'key1';
 *   value2: 'key2';
 * }
 */
type MappedTypeInverse = Inverse<MappedType>

---

我已经尝试了一些东西..但无济于事:

type Inverse<M> = M extends Record<infer O, infer T> ? Record<T, O> : never;

/**
 * type MappedTypeInverse = {
 *   value1: 'key1' | 'key2'
 *   value2: 'key2' | 'key2'
 * }
 */
type MappedTypeInverse = Inverse<MappedType>

type InverseValue<M extends Record<any, any>, V extends M[keyof M]> = V extends M[infer K] ? K : never;

/**
 * type MappedTypeInverseValue = unknown // expecting 'key1'
 */
type MappedTypeInverseValue = InverseValue<MappedType, 'value1'>

这可能吗？任何帮助将不胜感激!

Answer 1

这是一个精益alternative (除了帕特里克罗伯特的好解决方案):

type KeyFromVal<T, V> = {
  [K in keyof T]: V extends T[K] ? K : never
}[keyof T];

// we assume the type to be an object literal with string values
// , should also work with number or symbol
type Inverse<M extends Record<string, string>> = {
  [K in M[keyof M]]: KeyFromVal<M, K>
};

type MappedType = {
  key1: 'value1'
  key2: 'value2'
};

type MappedTypeInverse = Inverse<MappedType> // { value1: "key1"; value2: "key2"; }