index.js

let canvas = document.getElementById("c");
let ctx = canvas.getContext("2d");
let CANVAS_WIDTH = window.innerWidth;
let CANVAS_HEIGHT = window.innerHeight;
canvas.width = CANVAS_WIDTH;
canvas.height = CANVAS_HEIGHT;

let dots = [];

for (let i = 0; i < 50; i++) {
  dots.push(new Dot(Math.random() * CANVAS_WIDTH, Math.random() * CANVAS_HEIGHT));
}

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

  for (let d of dots) {
    d.update();
    d.constrain();
    d.render(ctx);
  }

  requestAnimationFrame(animate);
}
animate();