physics.js

const TIMESTEP = 10; // 100 updates per second => 10ms = 0.01s => 1frame / 0.01s = 100fps

function renderLoop() {

  // Do Renderer Things here

  window.requestAnimationFrame(renderLoop);
}

window.requestAnimationFrame(renderLoop)

var lastTime = Date.now();
var currentTick = 0;
function physicsLoop() {
  
  // We assume each tick has a deltaTime of TIMESTEP which may cause slowmotion if this is inefficient. 
  
  const now = Date.now();
  setTimeout(physicsLoop, Math.max(0, TIMESTEP - (now - lastTime)));
  lastTime = now;
  currentTick += 1;
}
             
physicsLoop();