如何在打字稿中使用promise.allSettled？

Question

Typescript 构建失败，因为它似乎不喜欢，Promise.allSetttled即使我已经设置了 ts config coilerOptions"lib": [ "ES2020.Promise" ],似乎 的响应promise.allSettled不包括resultor reason。运行 typescript build 时出现以下错误：Property 'reason' does not exist on type 'PromiseSettledResult<IMyPromiseResult>'.和Property 'value' does not exist on type 'PromiseRejectedResult'.我的代码块如下所示，正如您所看到的，我正在尝试访问reason每个result已解决的承诺。const myPromise = async () : Promise<IMyPromiseResult> {  return new Promise((resolve) => {    resolve("hello world")  })}const data = await Promise.allSettled([  myPromise()]);const response = data.find(res => res.status === 'fulfilled')?.result;if(!response) {  const error = data.find(res => res.status === 'rejected')?.reason;  throw new Error(error);}如何更新 Promise.allSettled 声明以包含正确的接口？

Answer 1

使用类型保护。比内联类型保护更优雅的解决方案是将它们定义为单独的函数，并且通过泛型绑定，您也可以获得已实现的承诺的正确值，并且可以重用以满足任何过滤需求allSettled。

不需要铸造（通常应该避免）。

const isRejected = (input: PromiseSettledResult<unknown>): input is PromiseRejectedResult => 

  input.status === 'rejected'

const isFulfilled = <T>(input: PromiseSettledResult<T>): input is PromiseFulfilledResult<T> => 

  input.status === 'fulfilled'

const myPromise = async () => Promise.resolve("hello world");

const data = await Promise.allSettled([myPromise()]);

const response = data.find(isFulfilled)?.value

const error = data.find(isRejected)?.reason

Answer 2

TypeScript 在检查类型时不知道类型是否为PromiseFulfilledResult/ PromiseRejectedResult。

唯一的办法就是铸造承诺的结果。之所以可以这样做，是因为您已经验证了已解决的承诺已实现或已拒绝。

看这个例子：

const myPromise = async (): Promise<string> => {

  return new Promise((resolve) => {

    resolve("hello world");

  });

};

const data = await Promise.allSettled([myPromise()]);

const response = (data.find(

  (res) => res.status === "fulfilled"

) as PromiseFulfilledResult<string> | undefined)?.value;

if (!response) {

  const error = (data.find(

    (res) => res.status === "rejected"

  ) as PromiseRejectedResult | undefined)?.reason;

  throw new Error(error);

}

Answer 3

使用类型保护：

const isFulfilled = <T,>(p:PromiseSettledResult<T>): p is PromiseFulfilledResult<T> => p.status === 'fulfilled';

const isRejected = <T,>(p:PromiseSettledResult<T>): p is PromiseRejectedResult => p.status === 'rejected';

const results = await Promise.allSettled(...);

const fulfilledValues = results.filter(isFulfilled).map(p => p.value);

const rejectedReasons = results.filter(isRejected).map(p => p.reason);

Answer 4

这让ts不生气。

const rawResponse = await Promise.allSettled(promiseArray);

const response = rawResponse.filter((res) => res.status === 'fulfilled') as PromiseFulfilledResult<any>[];

const result = response[0].value

Answer 5

将回调定义find为类型保护，返回类型谓词：

type IMyPromiseResult = string

const response = data.find(

  (res): res is PromiseFulfilledResult<string> => res.status === 'fulfilled'

)?.value;

if (!response) {

  const error = data.find(

    (res): res is PromiseRejectedResult => res.status === 'rejected'

  )?.reason;

  throw new Error(error);

}

演示游乐场