NodeJS client gameloop running slightly faster than server gameloop

Question

So I'm working on a real time multiplayer game in NodeJs (Client and Server). Both loops handle the same "physics" (movement at a constant rate) and both are running at 40hz or 40 times per second. I am using setInterval on both client and server with a delay of 40ms. The issue is that my server average delta between each tick is ~41 and my client average delta between each tick is ~40. This leads to results like this:

See in the last result, there is a difference of 46 ticks meaning the client is rendering about 1.8 seconds ahead of server time. My first guess on solving this is to sync the client every so often but that would lead to it "teleporting" backwards quite often due to how much it is desyncing.

Answer 1

Rather than coupling the time component of your physics engine with this abstract notion of a game loop tick, could you use the system time? One second on machine X will always be the same as one second on machine Y.

let currentTime = Date.getTime();

// Then in your loop
let previousTime = currentTime;
currentTime = Date.getTime();
let delta = currentTime - previousTime;