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PromiseAll

介绍​

给函数PromiseAll指定类型，它接受元素为 Promise 或者类似 Promise 的对象的数组，返回值应为Promise<T>，其中T是这些 Promise 的结果组成的数组。

例如

ts
  const promise1 = Promise.resolve(3);
  const promise2 = 42;
  const promise3 = new Promise<string>((resolve, reject) => {
    setTimeout(resolve, 100, 'foo');
  });
  // 应推导出 `Promise<[number, 42, string]>`
  const p = PromiseAll([promise1, promise2, promise3] as const)
ts
  const promise1 = Promise.resolve(3);
  const promise2 = 42;
  const promise3 = new Promise<string>((resolve, reject) => {
    setTimeout(resolve, 100, 'foo');
  });
  // 应推导出 `Promise<[number, 42, string]>`
  const p = PromiseAll([promise1, promise2, promise3] as const)
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起点​

ts
/* _____________ Your Code Here _____________ */
 
declare function PromiseAll(values: any): any
 
/* _____________ Test Cases _____________ */
const promiseAllTest1 = PromiseAll([1, 2, 3] as const)
const promiseAllTest2 = PromiseAll([1, 2, Promise.resolve(3)] as const)
const promiseAllTest3 = PromiseAll([1, 2, Promise.resolve(3)])
const promiseAllTest4 = PromiseAll<Array<number | Promise<number>>>([1, 2, 3])
Expected 0 type arguments, but got 1.2558Expected 0 type arguments, but got 1.
 
type cases = [
  Expect<Equal<typeof promiseAllTest1, Promise<[1, 2, 3]>>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
  Expect<Equal<typeof promiseAllTest2, Promise<[1, 2, number]>>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
  Expect<Equal<typeof promiseAllTest3, Promise<[number, number, number]>>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
  Expect<Equal<typeof promiseAllTest4, Promise<number[]>>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
]
 
ts
/* _____________ Your Code Here _____________ */
 
declare function PromiseAll(values: any): any
 
/* _____________ Test Cases _____________ */
const promiseAllTest1 = PromiseAll([1, 2, 3] as const)
const promiseAllTest2 = PromiseAll([1, 2, Promise.resolve(3)] as const)
const promiseAllTest3 = PromiseAll([1, 2, Promise.resolve(3)])
const promiseAllTest4 = PromiseAll<Array<number | Promise<number>>>([1, 2, 3])
Expected 0 type arguments, but got 1.2558Expected 0 type arguments, but got 1.
 
type cases = [
  Expect<Equal<typeof promiseAllTest1, Promise<[1, 2, 3]>>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
  Expect<Equal<typeof promiseAllTest2, Promise<[1, 2, number]>>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
  Expect<Equal<typeof promiseAllTest3, Promise<[number, number, number]>>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
  Expect<Equal<typeof promiseAllTest4, Promise<number[]>>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
]
 
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解决方案​

Spoiler warning // Click to reveal answer
ts
//方案1
declare function PromiseAll<T extends any[]>(values: readonly [...T]): Promise<{
  [K in keyof T]: Awaited<T[K]>
}>
 
ts
//方案1
declare function PromiseAll<T extends any[]>(values: readonly [...T]): Promise<{
  [K in keyof T]: Awaited<T[K]>
}>
 
ts
//方案2
declare function PromiseAll<T extends any[]>(values: readonly [...T]): Promise<{
  [K in keyof T]: T[K] extends Promise<infer R> ? R : T[K]
}>
 
ts
//方案2
declare function PromiseAll<T extends any[]>(values: readonly [...T]): Promise<{
  [K in keyof T]: T[K] extends Promise<infer R> ? R : T[K]
}>
 
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