等待对象内的 promise 解决

Question

我有一个以 promise 为值的对象。 对象字段可以具有不同类型的值，例如函数、承诺、字符串、数字或其他对象。 如何实现一个等待对象中所有承诺解决的函数？

 const asyncFunction = () => { return Promise.resolve("Resolved!") } const nonAsyncFunction = () => { return "Resolved!" } const awaitObjectWithPromise = (obj) => { // Returns a promise which waits for all // the promises inside "obj" to be resolved. } let obj = { key1: asyncFunction(), key2: nonAsyncFunction(), key3: "Some Value", parent1: { key1: asyncFunction(), key2: nonAsyncFunction(), key3: "Some Value" } } awaitObjectWithPromise(obj).then((obj) => { console.log(obj); // Should output: // { // key1: "Resolved!", // key2: "Resolved!", // key3: "Some Value", // parent1: { // key1: "Resolved!", // key2: "Resolved!", // key3: "Some Value" // } // } })

Answer 1

您可以遍历对象的键并解决承诺。

 const asyncFunction = () => { return Promise.resolve("Resolved!") } const nonAsyncFunction = () => { return "Resolved!" } const awaitObjectWithPromise = async(obj) => { for (let prop in obj) { // If the propriety has a 'then' function it's a Promise if (typeof obj[prop].then === 'function') { obj[prop] = await obj[prop]; } if (typeof obj[prop] === 'object') { obj[prop] = await awaitObjectWithPromise(obj[prop]); } } return obj; } let obj = { key1: asyncFunction(), key2: nonAsyncFunction(), key3: "Some Value", parent1: { key1: asyncFunction(), key2: nonAsyncFunction(), key3: "Some Value" } } awaitObjectWithPromise(obj).then((obj) => { console.log(obj); });

Answer 2

在接受的答案中，我对某些事情不满意：

• 如果其中一个字段为null或undefined ，则会引发错误；
• 输入值不能是 Promise；
• 缺乏等待 Promise 的并行性；

为了解决这些问题，我更改了函数：

const promiseAll = async (obj) => {
    if (obj && typeof obj.then == 'function') obj = await obj;
    if (!obj || typeof obj != 'object') return obj;
    const forWaiting = [];
    Object.keys(obj).forEach(k => {
        if (obj[k] && typeof obj[k].then == 'function') forWaiting.push(obj[k].then(res => obj[k] = res));
        if (obj[k] && typeof obj[k] == 'object') forWaiting.push(promiseAll(obj[k]))
    });
    await Promise.all(forWaiting);
    return obj;
}

也许对某人来说，它会很有用。