JavaScript 结合 CSS3 实现动态星星海背景特效

var 宽 = document.documentElement.clientWidth;
var 高 = document.documentElement.clientHeight;

appendChild()

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>Title</title>
 <script src="UnderScore.js"></script>
 <style>
  *{margin: 0;padding-top: 0}
  body{background-color: #000}
  span{
   width: 30px;
   height: 30px;
   background: url("star.png") no-repeat;
   position: absolute;
   background-size: contain;
   animation: flash 1s alternate infinite;
  }
  @keyframes flash{
   0%{opacity: 0}
   25%{opacity: 0.25}
   50%{opacity: 0.5}
   75%{opacity: 0.75}
   100%{opacity: 1}
  }
  span:hover{
   transform: scale(3, 3) rotate(180deg) !important;
   transition: all 1s;
  }
 </style>
</head>
<body>
<script>
 window.onload = function (ev) {
  // 1. 求出屏幕尺寸
  var screenWidth = document.documentElement.clientWidth;
  var screenHeight = document.documentElement.clientHeight;

  // 2. 动态创建10颗星星
  for (var i = 0; i < 200; i++) {
   // 2.1 创建星星
   var span = document.createElement('span');
   document.body.appendChild(span);

   // 2.2 随即坐标
   var x = parseInt(_.random(0, screenWidth));
   var y = parseInt(_.random(0, screenHeight));
   span.style.left = x +'px';
   span.style.top = y + 'px';

   // 2.3 随机缩放
   var scale = _.random(0, 1.5);
   span.style.transform = 'scale('+scale+','+scale+')';

   // 2.4 频率
   var rate = _.random(0, 1.5);
   span.style.animationDelay = rate + 's';
  }
 }
</script>
</body>
</html>