Simple mutex for JavaScript

simple_mutex.ts

class SimpleMutex {
  _lock: boolean;
  _resolves: Array<() => void>;

  constructor() {
    this._lock = false;
    this._resolves = [];
  }

  async synchronize(callback: () => Promise<any>) {
    try {
      await this.lock();
      await callback();
    } finally {
      this.unlock();
    }
  }

  async lock() {
    if (this._lock) {
      const that = this;
      await new Promise<void>((resolve, _) => {
        that._resolves.push(resolve);
      });
    } else {
      this._lock = true;
    }
  }

  unlock() {
    this._lock = false;
    this._resolves.forEach((resolve) => resolve());
    this._resolves = [];
  }
}