title: requestAnimationFrame vs EventListener, concurrent or consecutive
body: <p>I have a <code>requestAnimationFrame</code> loop and multiple EventListeners (for keyboard/mouse).</p>
  <p>Am I guaranteed the functions they call will always run 1 after the other, or is there a chance they will sometimes run concurrently?</p>
  <pre class="lang-js prettyprint-override"><code>function f1() {
    ...
  }
  document.addEventListener('keydown', f1)
  
  ...
  
  function f2() {
    ...
    requestAnimationFrame(f2)
  }
  requestAnimationFrame(f2)
  </code></pre>