a.js

import Bacon from 'baconjs';
import fetch from 'node-fetch';

const makeRequest = () => fetch('https://wtfismyip.com/text');

const createThrottler = (onValue, maxConcurrencyInWindow = 5, windowLength = 5000) => {
  const bus = new Bacon.Bus();
  bus.flatMapWithConcurrencyLimit(maxConcurrencyInWindow, fn => (
    Bacon.fromPromise(fn()).concat(Bacon.later(windowLength).filter(false))
  )).onValue(onValue);

  return fn => bus.push(fn);
}

const throttle = createThrottler(res => res.text().then(text => console.log(text.trim())));
Array(30).fill(() => makeRequest()).forEach(fn => throttle(fn));