Expanding on an idea from https://www.matteoagosti.com/blog/2013/01/22/rate-limiting-function-calls-in-javascript/ to return Promises

rateLimit.js

exports.RateLimit = (function () {
  var RateLimit = function (maxOps, interval, allowBursts) {
    this._maxRate = allowBursts ? maxOps : maxOps / interval;
    this._interval = interval;
    this._allowBursts = allowBursts;

    this._numOps = 0;
    this._start = new Date().getTime();
    this._queue = [];
  };

  RateLimit.prototype.schedule = function (fn) {
    var that = this,
      rate = 0,
      now = new Date().getTime(),
      elapsed = now - this._start;

    if (elapsed > this._interval) {
      this._numOps = 0;
      this._start = now;
    }

    rate = this._numOps / (this._allowBursts ? 1 : elapsed);

    if (rate < this._maxRate) {
      if (this._queue.length === 0) {
        this._numOps++;
        return Promise.resolve(fn());
      } else {
        if (fn) this._queue.push(fn);

        this._numOps++;
        return Promise.resolve(this._queue.shift()());
      }
    } else {
      if (fn) this._queue.push(fn);

      return new Promise((resolve, reject) =>
        setTimeout(function () {
          resolve(that.schedule());
        }, 1 / this._maxRate)
      );
    }
  };

  return RateLimit;
})();