The idea was to match animation speed of the gif and JavaScript implementation (which was 24 frames per second)

requestAnimationFrame() (RAF) is more likely to fire approximately 60 times per second than setTimeout(..., 1000 / 60) would. But I needed 1000 / 24, and setTimeout worked very well, so I used it.

If I were doing it all over again, I'd probably use RAF with window.performance, or simple counting variable as a timer. RAF is indeed much smoother than setTimeout and on top of it, RAF saves battery life when a user doesn't have your page open.

Good question!