Don't read Math all the time

[rbdr/r.bdr.sh] / js / animation.js

(function () {

  var canvas = document.querySelector('canvas'),
      context = canvas.getContext('2d'),
      fps = 30,
      lastFrame = 0,
      speed = 1,
      size = 5 + rand(10),
      r = Math.random,
      pi = Math.PI;

  var clear = !!(r() > 0.5);
  var changeColor = !!(r() > 0.5);
  var items = Array(rand(10) + 6).fill(null).map(() => ({
    x: rand(64),
    y: rand(64),
    angle: r() * 2 * pi,
    color: Array(3).fill(rand(256))
  }));
  var shapes = [square, circle, heart, chaos, lineChaos];
  var positions = [identity, spin(5), spin(15)];
  var draw = shapes[rand(shapes.length)];
  var position = positions[rand(positions.length)];

  function rand (x) {
    return Math.floor(r() * x);
  }

  function square(item) {

    var p = position(item);
    context.fillRect(p.x, p.y, size, size);
  }

  function circle(item) {

    var p = position(item);
    context.beginPath();
    context.arc(p.x, p.y, size / 2, 0, 2 * pi);
    context.fill();
  }

  function chaos(item) {

    var p = position(item);
    context.beginPath();
    context.moveTo(p.x, p.y);
    context.lineTo(p.x * 10 * Math.cos(item.angle), p.y * 10 * Math.sin(item.angle));
    context.lineTo(rand(64), rand(64));
    context.fill();
  }

  function lineChaos(item) {

    var p = position(item);
    context.beginPath();
    context.lineWidth = 5;
    context.strokeStyle = `rgb(${item.color.join(',')})`;
    context.moveTo(p.x, p.y);
    context.lineTo(p.x * 10 * Math.cos(item.angle), p.y * 10 * Math.sin(item.angle));
    context.stroke();
  }

  function square(item) {

    var p = position(item);
    context.fillRect(p.x, p.y, size, size);
  }

  function heart(item) {

    var p = position(item);
    context.fillRect(p.x, p.y, size, size);

    context.beginPath();
    context.arc(p.x + size / 2, p.y, size / 2, 0, 2 * pi, false);
    context.fill();
    context.closePath();

    context.beginPath();
    context.arc(p.x + size, p.y + size / 2, size / 2, 0, 2 * pi, false);
    context.fill();
    context.closePath();
  }

  function identity(position) {

    return position;
  }

  function spin(radius) {
    return function (position) {

      return {
        x: position.x + radius * Math.cos(lastFrame),
        y: position.y + radius * Math.sin(lastFrame)
      }
    }
  }

  function move(item) {

    item.x = item.x + speed * Math.cos(item.angle);
    item.y = item.y + speed * Math.sin(item.angle);

    if (item.x < 0 || item.x > 64) {
      item.angle = Math.atan2(Math.sin(item.angle), -Math.cos(item.angle))
    }

    if (item.y < 0 || item.y > 64) {
      item.angle = Math.atan2(-Math.sin(item.angle), Math.cos(item.angle))
    }
  }

  function updateColor(item) {

    item.color = item.color.map((c) => {
      c = c + 5;
      return c > 255 ? 0 : c;
    })
  }

  function frame(time) {

    window.requestAnimationFrame(frame);

    var delta = time - lastFrame;

    if (delta > 1000 / fps) {
      clear && context.clearRect(0, 0, 64, 64);
      for (var item of items) {
        context.fillStyle = `rgb(${item.color.join(',')})`;
        draw(item);
        changeColor && updateColor(item);
        move(item);
      }

      lastFrame = time;
    }
  }

  frame();
}
)();