dnssd/src/Mutex.js

Bonjour/Avahi-like service discovery in pure JavaScript

/**
 * const mutex = new Mutex();
 *
 * function limitMe() {
 *   mutex.lock((unlock) => {
 *     asyncFn().then(unlock);
 *   });
 * }
 *
 * limitMe();
 * limitMe(); // <-- will wait for first call to finish & unlock
 *
 */
class Mutex {
  constructor() {
    this._queue = [];
    this.locked = false;
  }

  lock(fn) {
    const unlock = () => {
      const nextFn = this._queue.shift();

      if (nextFn) nextFn(unlock);
      else this.locked = false;
    };

    if (!this.locked) {
      this.locked = true;
      fn(unlock);
    } else {
      this._queue.push(fn);
    }
  }
}

module.exports = Mutex;