lovecoding
/
VIP20


			
				
					
						
						
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							<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    img{
      position: absolute;
    }
  </style>
</head>
<body>
  <script>
    //获取屏幕的宽度
    var screenWidth = document.body.clientWidth || document.documentElement.clientWidth
    //获取屏幕的高度
    var screenHeight = document.body.clientHeight || document.documentElement.clientHeight
    //构造函数  写属性
    function leaf(){
      this.width = Math.random() * 100 + 100
      //screenWidth - this.width  最大的距离
      this.xLeft = Math.random() * (screenWidth - this.width)
      this.xTop = 0
      //Math.random()  0->1 之间的随机小数
      //'img/1.png'
      // 1 - 4 随机整数
      //Math.random() * 4  0->4 之间的随机小数  不包括4
      //Math.random() * 4 + 1    1->5之间的随机小数  不包括5
      //Math.floor()   向下取整

      //Math.floor(Math.random() * 4 + 1)  1->5之间的随机小数向下取整  1 2 3 4

      this.bg = 'img/'+ Math.floor(Math.random() * 4 + 1) +'.png'
    }

    //原型下面 写方法
    //<img src="">
    leaf.prototype.init = function(){
      var oImg = document.createElement('img')
      oImg.src = this.bg
      oImg.style.width = this.width + 'px'
      oImg.style.left = this.xLeft + 'px'
      oImg.style.top = this.xTop + 'px'
      this.img = oImg
      document.body.appendChild(oImg)
    }
    //下落的方法
    leaf.prototype.fall = function(){
      setTimeout(function(){
        this.timer = setInterval(function(){
          console.log(this) //window  .bind(this) this->leaf
          if(this.img.offsetTop < screenHeight - this.img.offsetHeight){
            this.img.style.top = this.img.offsetTop + 10 + 'px'
          } else{
            clearInterval(this.timer)
          }
        }.bind(this),20)
        // console.log(this) // window  .bind(this)  this-> leaf
      }.bind(this),Math.random()*2000)
      // console.log(this) // leaf
    }
    var leafArr = [];
    for(var i=0;i<20;i++){
      //创建实例化对象
      var leaf1 = new leaf()
      leaf1.init()
      leafArr.push(leaf1)
    }
    document.onclick = function(){
      for(var i=0;i<leafArr.length;i++){
        leafArr[i].fall()
      }
    }
  </script>
</body>
</html>