js代码

<script type="text/javascript">
(function() {
  var c1 = document.getElementById("c1");
  var c2 = document.getElementById("c2");
  var ctx1 = c1.getContext("2d");
  var ctx2 = c2.getContext("2d");
  c1.height = 300;
  c1.width = 300;
  c2.height = 300;
  c2.width = 300;

  ctx1.fillStyle = "white";
  ctx2.fillStyle = "white";
  var c1Flakes = [];
  var c2Flakes = [];

  function Flake(r) {
    this.x = Math.random() * 300;
    this.y = Math.random() * 250;
    this.r = r;
  }

  for (var i = 0; i <= 80; i++) {
    var flake = new Flake(2);
    c1Flakes.push(flake);
  }

  for (var i = 0; i <= 80; i++) {
    var flake = new Flake(3);
    c2Flakes.push(flake);
  }

  function render() {
    ctx1.clearRect(0, 0, 300, 300);
    ctx2.clearRect(0, 0, 300, 300);
    for (var i = 0; i < c1Flakes.length; i++) {
      ctx1.beginPath();
      ctx1.arc(c1Flakes[i].x, c1Flakes[i].y, c1Flakes[i].r, 0, Math.PI * 2);
      ctx1.fill();
      if (c1Flakes[i].y <= 245){
      c1Flakes[i].y+= .3;
      }
      else{
        c1Flakes[i].y = 0;
      }
    }

    for (var i = 0; i < c2Flakes.length; i++) {
      ctx2.beginPath();
      ctx2.arc(c2Flakes[i].x, c2Flakes[i].y, c2Flakes[i].r, 0, Math.PI * 2);
      ctx2.fill();
      if (c2Flakes[i].y <= 245){
      c2Flakes[i].y += .6;
      }
      else{
        c2Flakes[i].y = 0;
      }
    }
    requestAnimationFrame(render);
  }
  render();
})();
</script>