Raf throttle a function

rafThrottle.js

// Comparison b/w rx-raf-throttle and myRafThrottle
// Copy-paste at https://esnextb.in to run
// Expected output is both fn get called together roughly

import {Observable as O} from 'rx'
import {rxRAFThrottle} from 'rx-raf-throttle'

const rafThrottle = f => {
  let rendering = false
  let _val

  const callback = () => {
    rendering = true
    f(_val)
    rendering = false
  }

  return val => {
    _val = val
    if (!rendering) {
      requestAnimationFrame(callback)
    }
  }
}

const INTERVAL = 1 // in ms

const t = O.interval(INTERVAL)
const helper = fn => {
  let counter = 0
  const timer = setInterval(() => {
    fn(counter)
    counter++
  }, INTERVAL)
}

t.subscribe(x => document.writeln(x + '<br/>'))
helper(x => document.writeln(x + '<br/>'))

rxRAFThrottle(t).subscribe(x => document.writeln('rxRaf(' + x + ')<br/>'))
helper(rafThrottle(x => document.writeln('myRaf(' + x + ')<br/>')))