如何等待JavaScript/TypeScript中的Promises列表? [英] How do I await a list of Promises in JavaScript/TypeScript?

问题描述

我有以下代码，fileStatsPromises是Promise<Stats>[]，foo和bar都是Promise<Stats>[].等待他们的正确方法是什么?我想得到<Stats>[].

I have following code, fileStatsPromises is of Promise<Stats>[], both foo and bar are Promise<Stats>[]. What is the correct way to await them? I want to get <Stats>[].

    const files = await readDir(currentDir);
    const fileStatsPromises = files.map(filename => path.join(currentDir, filename)).map(stat);

    const foo = await fileStatsPromises;
    const bar = await Promise.all(fileStatsPromises);

一个最小的例子.

function makePromise() {
    return Promise.resolve("hello");
}
const promiseArray = [];
// const promiseArray = [] as Promise<string>[];
for (let i = 0; i < 10; i++) {
    promiseArray.push(makePromise());
}

(async () => {
    const foo = await promiseArray;
    const bar = await Promise.all(promiseArray);
})();

推荐答案

这是正确的:

const bar = await Promise.all(promiseArray);

await Promise.all([...])接受一个Promises数组并返回一个结果数组.

await Promise.all([...]) takes an array of Promises and returns an array of results.

bar将是一个数组:['hello', ..., 'hello']

您还可以解构所得数组:

You can also deconstruct the resulting array:

const [bar1, ..., bar10] = await Promise.all(promiseArray);
console.log(bar1); // hello
console.log(bar7); // hello

这篇关于如何等待JavaScript/TypeScript中的Promises列表?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！