异步并发控制，曾经某郭姓男子问的【存档备份】

create-async-worker.ts

type Task<T> = () => (T | Promise<T>);
type UnLock = () => void;

class ProcessLock {
  private count = 0;
  private queue: UnLock[] = [];
  constructor(public capacity: number) {}
  request = async (): Promise<UnLock> => {
    if (this.count >= this.capacity) {
      await new Promise<void>((resolve) => {
        this.queue.push(resolve);
      });

      return this.request();
    }

    this.count = this.count + 1;
    return () => {
      this.count = this.count - 1;
      this.queue.shift()?.(); // 这里不能是 pop 哦, 要执行最早进来的任务
    }
  }
}

/**
 * 异步并发控制器
 */
export function createAsyncWorker(capacity: number): <T>(task: Task<T>) => Promise<T> {
  const plock = new ProcessLock(capacity);

  // show me your code
  return async function<T>(task: Task<T>): Promise<T> {
    const release = await plock.request(); // 申请一下资源, 没有的话就等
    try {
      const result = await task(); // 跑任务
      release(); // 不要忘记释放哦
      return result; // 返回结果
    } catch (error) {
      release(); // 出错了也要释放哦
      throw error;
    }
  };
}