飘舞的小球

<!DOCTYPE html>
<html>
 <head>
  <meta charset="utf-8">
  <title>飘舞的小球</title>
  <style type="text/css">
   div {
    width: 100px;
    height: 100px;
    line-height: 100px;
    font-size: 30px;
    border-radius: 50px;
    background-color: cyan;
    text-align: center;
    position: absolute;
    left: 0;
    top: 0;
   }
  </style>
 </head>
 <body>
  <div id="piao">飘啊飘</div>
 </body>
 <script type="text/javascript">
  // 设置变化速度
  var xSpeed = 10
  var ySpeed = 20
  // 获取变量
  var piao = document.getElementById('piao')
  // 获取尺寸
  var width = parseInt(getComputedStyle(piao)['width'])
  var height = parseInt(getComputedStyle(piao)['height'])
  // 设置周期定时任务
  var timer = setInterval(function() {
   // 获取当前位置
   var left = parseInt(getComputedStyle(piao)['left'])
   var top = parseInt(getComputedStyle(piao)['top'])
   // 设置新的位置
   left += xSpeed
   top += ySpeed
   // 对当前位置进行判定,防止小球跑出边界
   if (left <= 0 || left + width >= window.innerWidth) {
    xSpeed *= -1
   }
   if (top <= 0 || top + height >= window.innerHeight) {
    ySpeed *= -1
   }
   // 写入位置
   piao.style.left = left + 'px'
   piao.style.top = top + 'px'
  },100)
 </script>
</html>

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转载自www.cnblogs.com/wenjiangtao/p/10718671.html