这段 js 代码的解释

最近给我的 yimuc.com 整了个工具集的新功能，在搜寻工具库的时候发现了这个库async-pool。我自己工具站地址是这个：job.yimuc.com/online/toolkit ，介意的请不要点过去哈，浪费你时间。

重点在这里，先上个 Github 电梯直达： https://github.com/rxaviers/async-pool/blob/master/lib/es9.js

不跳转也行，整个库就只有这一段代码，代码我也直接贴下面：

async function* asyncPool(concurrency, iterable, iteratorFn) {
  const executing = new Set();
  async function consume() {
    const [promise, value] = await Promise.race(executing);
    executing.delete(promise);
    return value;
  }
  for (const item of iterable) {
    // Wrap iteratorFn() in an async fn to ensure we get a promise.
    // Then expose such promise, so it's possible to later reference and
    // remove it from the executing pool.
    const promise = (async () => await iteratorFn(item, iterable))().then(
      value => [promise, value]
    );
    executing.add(promise);
    if (executing.size >= concurrency) {
      yield await consume();
    }
  }
  while (executing.size) {
    yield await consume();
  }
}

module.exports = asyncPool;

感觉这样处理很优雅啊，代码也很简洁。因为我正常写业务代码很少用generator function的，所以看了会觉得很新颖，他这里用了Promise、async await、generator function，外层调用它的时候还可以用for await()。

学到了~

realJamespond

249 天前

刚好昨天撸了个类似的
```
export type Task = { (name: string): Promise<void> };
export async function queueStart(tasks: Task[], size = 1) {
const queue = (function* () {
for (let i = 0; i < tasks.length; i++) {
yield tasks[i];
}
})();
let finished = false;
const handle = async (name: string) => {
for (;;) {
const { done, value: task } = queue.next();
if (done) {
finished = true;
}
if (finished) {
break;
} else if (task) {
await task(name);
}
}
};
const joinAll: Promise<void>[] = [];
for (let i = 0; i < size; i++) {
const name = `thread-${i}`;
const join = handle(name).then(() => {
console.log(name, "end", new Date().toLocaleTimeString());
});
joinAll.push(join);
}
// return Promise.all(joinAll);
for (const join of joinAll) {
await join;
}
}

export function getTask(promise: Promise<unknown>): Task {
return async (name) => {
const begin = Date.now()
console.log(name, "task begin");
await promise;
console.log(name, "task done", (Date.now() - begin)*0.001);
};
}

// getTask(Promise.resolve(1))
// getTask(Promise.resolve("abc"))
// getTask(Promise.resolve({}))
```