javascript - 无法访问 Promise.all 数组后已解决的 Promise 的值

Question

这个问题已经有答案了:

Promise.all in JavaScript: How to get resolve value for all promises? (2 个回答)

How can I access the value of a promise? (14 个回答)

How to fetch value from Promise object after promise has been resolved (2 个回答)

已关闭 4 年前。

在 Promise.all 之后无法访问已解决的 Promise 的值。正如您在下面的示例中看到的，res.prop打印未定义。我想我可以创建一个包装函数，将解析的值推送到另一个 responses数组，但这似乎不是一个干净的方法。

(async () => {
    const responses = []

    let counter = 10
    while (counter--) {
      responses.push(new Promise(resolve => resolve({prop: 10})))
    }

    await Promise.all(responses)

    for (const res of responses) {
        console.log(res) // -> prints Promise {prop: 10}
        console.log(res.prop) // -> prints undefined
    }
})()

Answer 1

你永远不会使用await Promise.all(responses)的返回值。您的 Promise 的返回值由 Promises.all 返回:

(async () => {
    const responses = []

    let counter = 10
    while (counter--) {
      responses.push(new Promise(resolve => resolve({prop: 10})))
    }

    const results = await Promise.all(responses)

    for (const res of results) {
        console.log(res) // -> prints Promise {prop: 10}
        console.log(res.prop) // -> prints undefined
    }
})()