How does splitting the game FPS and Sprite FPS work?

[Jambutters]

Noob to game dev here, this is more of a general javascript question but:

I'm looking over kittykatattacks spriteUtilities library and

var frameRate = 1000 / sprite.fps;

        //Set the sprite to the starting frame
        sprite.gotoAndStop(startFrame);

        //Set the `frameCounter` to the first frame
        frameCounter = 1;

        //If the state isn't already `playing`, start it
        if (!sprite.animating) {
timerInterval = setInterval(advanceFrame.bind(this), frameRate);
}

 

So how does this(the sprites fps) not conflict with the games fps? Generally you have the main game update loop somewhere that's also a setInterval(gameLoop, fps).
and javascript is synchronous right?

[xerver]

Yes, JS is a synchronous event loop; but not everything has to run every loop. Similarly if the "fps" of the sprite is faster than display that is OK too since we will just calculate what frame to show not actually simulate each "sprite frame".

[Taz]

You can change the sprite's texture and other properties as often as you like, but render is still called at the same rate* (render handles all of the actual drawing to screen). On the other hand, if you were updating the same property at two different time intervals that could be problematic.

*well, assuming your interval functions finish quickly enough, etc. That's a different issue thou..