InMemoryCounter

InMemoryCounter.js

class InMemoryCounter {
  constructor({ seconds = 1, rolling = true, max }) {
    this.seconds = seconds;
    this.rolling = rolling;
    this.max = max;

    if (!this.rolling) {
      this.interval = setInterval(() => {
        this.counter = 0;
      }, this.seconds * 1000);
    }

    this.counter = 0;
  }

  increment() {
    if (this.max !== undefined && this.counter >= this.max) {
      return false;
    }

    this.counter++;

    if (this.rolling) {
      setTimeout(() => {
        this.counter = Math.max(0, this.counter - 1);
      }, this.seconds * 1000);
    }

    return true;
  }

  count() {
    return this.counter;
  }

  remaining() {
    if (this.max === undefined) {
      throw new Error("Missing 'max' config");
    }

    return Math.max(0, this.max - this.counter);
  }
  
  stop() {
    clearInterval(this.interval);
  }
}

// Use InMemoryCounter as a rate limiter. 10 increments per 2 seconds rolling.
const rateLimiter = new InMemoryCounter({ seconds: 2, rolling: true, max: 10 });
rateLimiter.increment(); // true
rateLimiter.remaining(); // 9

// Use InMemoryCounter as an FPS counter. Hard reset every second.
const fpsCounter = new InMemoryCounter({ seconds: 1, rolling: false });
fpsCounter.increment(); // true
fpsCounter.count(); // 1
fpsCounter.stop();