index.js

const ITERATION = 100; // max physics iterations per frame

function animate() {
  ctx.clearRect(0, 0, CANVAS_WIDTH, CANVAS_HEIGHT);

  // update 
  for (let i = 0; i < ITERATION; i++) {
    for (let d of dots) {
      d.constrain();        
    }
    for (let s of sticks) {
      s.update();
    }
  }
  
  for (let d of dots) {
    d.update();
    d.render(ctx);
  }
  for (let s of sticks) {
    s.update();
    s.render(ctx);
  }

  requestAnimationFrame(animate);
}
animate();