requestAnimation

getPinStyleAnimation.js

function getPinStyle (pin, scrollPosition) {
  // do some calculation based on the pin that was passed in and the current scroll position
  return { rotate, scale, translate }
}

requestAnimationFrame(function frame () {
  pins.forEach(pin => applyPinStyles(pin, getPinStyle(pin, window.scrollTop)))
  requestAnimationFrame(frame)
})

// `requestAnimationFrame` in this context saves you from a certain kind of bug in `setInterval`, 
// which is that `setInterval` calls are scheduled based on the computer clock (loosely speaking) 
// while `rAF` schedules the next call subsequent to the previous call.
//But `setInterval` can occasionally drop frames (IIRC), or stack frames within the same event loop turn. 
// It’s a bit of a consistency nightmare.