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)?.valueconst 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 = stringconst response = data.find(&nbsp; (res): res is PromiseFulfilledResult<string> => res.status === 'fulfilled')?.value;if (!response) {&nbsp; const error = data.find(&nbsp; &nbsp; (res): res is PromiseRejectedResult => res.status === 'rejected'&nbsp; )?.reason;&nbsp; throw new Error(error);}演示游乐场