hit-counter.js

class HitCounter {
  constructor(interval) {
    this.interval = interval;
    this.buckets = Array(60 / this.interval).fill(0);
    this.bucketCleanerInterval = this.initBucketCleaner();
  }

  count() {
    const bucket = this.getCurrentBucket();
    return this.buckets[bucket] += 1;
  }

  getCount() {
    const bucket = this.getCurrentBucket();
    return this.buckets[bucket];
  }

  stop() {
    clearInterval(this.bucketCleanerInterval);
  }

  getCurrentBucket() {
    const minutes = (new Date()).getMinutes();
    return Math.floor(minutes / this.interval);
  }

  initBucketCleaner() {
    const interval = 60 * this.interval * 1000 / 2;
    return setInterval(this.cleanBuckets.bind(this), interval);
  }

  cleanBuckets() {
    const bucket = this.getCurrentBucket();
    for (let interval = 0; interval < this.buckets.length; interval++) {
      if (interval !== bucket) this.buckets[interval] = 0;
    }
  }
}

module.exports = HitCounter;

if you are building a website, how do you count the number of visitors for the past 1 minute?
Above is the basic implementation