如何将Promise.reach或Promise.all与异步可迭代对象一起使用?

把每一个 for await 转换为异步IIFE,这样你就可以从每个IIFE中得到一个Promise。然后你可以打电话 Promise.all 或 Promise.race 在他们身上:

proc.stdout.setEncoding('utf8');
proc.stderr.setEncoding('utf8');
const stdoutProm = (async () => {
  for await (const data of proc.stdout) {
    console.log(new Date() - start, "proc stdout:", data);
  }
})();
const stderrProm = (async () => {
  for await (const data of proc.stderr) {
    console.log(new Date() - start, "proc stderr:", data);
  }
})();
await Promise.race([stdoutProm, stderrProm]);
// One of the iterators has been completely consumed

你也可以将这两个迭代器合并为一个:

 async function* combine(a, b) {
   a = a[Symbol.iterator](); b = b[Symbol.iterator]();
   let doneA = false, doneB = false;
   let itA = a.next().then(a => ({ a })),
          itB = b.next().then(b => ({ b }));
   while(true) {
      const result = await Promise.race([itA, itB]);
      doneA = doneA || result.a && result.a.done;
      doneB = doneB || result.b && result.b.done;
      if(doneA && doneB) return;
      yield [result.a && result.a.value, result.b && result.b.value];

      if(result.a) itA = a.next().then(a => ({ a }))
      else itB = b.next().then(b => ({ b }));
   }
}

可用作:

 for await(const [out, err] of combine(std.out, std.err)) {
   if(out) console.log(out);
   if(err) console.log(err);
 }