semaphore.js

class Semaphore {
    constructor(max = 1) {
        if (max < 1) { max = 1; }
        this.max = max;
        this.count = 0;
        this.queue = [];
    }
    acquire() {
        let promise;
        if (this.count < this.max) {
            promise = Promise.resolve();
        } else {
            promise = new Promise(resolve => {
                this.queue.push(resolve);
            });
        }
        this.count++;
        return promise;
    }
    release() {
        if (this.queue.length > 0) {
            const resolve = this.queue.shift();
            resolve();
        }
        this.count--;
    }
}

also a mutex

class Mutex {
  constructor() {
    this.locking = Promise.resolve();
  }

  async acquire() {
    let releaseNext;

    const lock = new Promise((resolve) => {
      releaseNext = resolve;
    });

    const release = this.locking.then(() => releaseNext);
    this.locking = this.locking.then(() => lock);

    return release;
  }
}