Promise.all vs await Promise.all例子错误

Question

我试图看到自己之间的不同。Promise.all 和 await Promise.all. 我了解到，如果其中一个承诺失败，第一个承诺就会提前结束，但在同样的情况下，对于 await，我们必须等待所有承诺的完成。

在我的例子中，在这两种情况下，它们同时结束。我做错了什么？

/**
 * Create a promise
 * @param ok true -> resolve, false -> reject
 */
function create_promise(ok) {
  return new Promise((resolve, reject) => {
    setTimeout(() => ok ? resolve() : reject(), 2e3)
  })
}

// Finish as soon as I get a reject
Promise.all([create_promise(true), create_promise(false), create_promise(true)])
  .catch(() => console.log('rejected'))

// Finish after waiting all
const my_async_function = async () => 
  await Promise.all([create_promise(true), create_promise(false), create_promise(true)])

my_async_function().catch(() => console.log('rejected'))

Answer 1

await Promise.all 将确保所有的承诺都被解决，然后再执行后面的行 await.

/**
 * Create a promise
 * @param ok true -> resolve, false -> reject
 */
function create_promise(ok) {
  return new Promise((resolve, reject) => {
    setTimeout(() => ok ? resolve() : reject(), 2e3)
  })
}

console.log("async/await version...")
const my_async_function = async () => {
  console.log("before await promise.all");
  const res = await Promise.all([create_promise(true), create_promise(false), create_promise(true)]);
  console.log("after await  promise.all"); // This line will be executed only after all promises are successfully resolved
  return res;
  }
my_async_function().catch(() => console.log('rejected'))

console.log("without async/await version...")
const my_SYNC_function = () => {
  console.log("before promise.all");
  const res = Promise.all([create_promise(true), create_promise(false), create_promise(true)]);
  console.log("after promise.all"); // This line will always be immediately executed after the Promise.all line, and not waiting for the promise completion  at all.
  return res; // So this line returns the return value of Promise.all, which will be an unresolved promise because the 2 seconds have not been elapsed yet.
  }
  
my_SYNC_function().catch(() => console.log('rejected'))

这与承诺本身在某种程度上 "执行得更快 "没有关系。

然而， 函数，调用 Promise.all 橆 await 返回的时间比较早，它只是返回一些Promise 悬而未决.