js实战之-碰撞运动

  1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
  2 <html xmlns="http://www.w3.org/1999/xhtml">
  3 <head>
  4 <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
  5 <title>js-碰撞运动</title>
  6 <style type="text/css">
  7 * { padding: 0; margin: 0; }
  8 ul,li{ list-style:none}
  9 .box{ width:100px; height:100px; background:#FF0000 ; position:absolute; top:100px; left:100px}
 10 </style>
 11 
 12 <script type="text/javascript">
 13 
 14 window.onload=function(){
 15     
 16     var speedX=0,speedY=0;
 17     var lastX=0,lastY=0;
 18     var timer=null;
 19     var obj=document.getElementById("box");
 20 
 21      obj.onmousedown=function(e){
 22            var e=e||window.event;
 23            var disX=e.clientX-obj.offsetLeft;
 24            var disY=e.clientY-obj.offsetTop;
 25            document.onmousemove=function(e){
 26                clearInterval(timer);
 27                var e=e||window.event;
 28                var l=e.clientX-disX;
 29                var t=e.clientY-disY;
 30                obj.style.left=l+"px";
 31                 obj.style.top=t+"px"; 
 32                 speedX=l-lastX;
 33                 speedY=t-lastY;
 34                 lastX=l;
 35                 lastY=t;
 36                
 37            }
 38          
 39           document.onmouseup=function(){
 40               
 41               document.onmousemove=null;
 42               document.onmouseup=null;
 43               objMove();
 44               
 45               return false;
 46   
 47          }
 48 
 49          return false;
 50      
 51     }
 52     
 53     
 54 function  objMove(){
 55     
 56 
 57     timer=setInterval(function(){
 58         
 59            speedY+=5;
 60               
 61            var l=obj.offsetLeft+speedX;
 62            var t=obj.offsetTop+speedY;    
 63     
 64            if(t>=document.documentElement.clientHeight-obj.offsetHeight){
 65                t=document.documentElement.clientHeight-obj.offsetHeight;
 66     
 67                  speedY*=-0.8;
 68                  speedX*=0.8;
 69            }
 70            if(t<=0){
 71                t=0;
 72                speedY*=-1;
 73              speedX*=0.8;
 74                
 75             }    
 76            if(l>=document.documentElement.clientWidth-obj.offsetWidth){
 77                 l=document.documentElement.clientWidth-obj.offsetWidth;
 78                 speedX*=-0.8;
 79                  
 80            }
 81            if(l<=0){
 82                
 83                l=0;
 84                speedX*=-0.8;
 85                 
 86            }    
 87            if(Math.abs(speedX)<1){
 88                
 89                speedX=0;
 90                
 91           }
 92            if(Math.abs(speedY)<1){
 93                
 94                speedY=0;
 95                
 96           }
 97           if(speedX==0&&speedY==0&& t==document.documentElement.clientHeight-obj.offsetHeight){
 98               
 99               clearInterval(timer);
100             
101               
102           }
103 
104            obj.style.left=l+"px";
105            obj.style.top=t+"px";        
106         
107       },30);
108       
109       
110 }          
111       
112       
113       
114 
115 }
116 
117 
118 
119 </script>
120 </head>
121 <body>
122 <div class="box" id="box"></div>
123 </body>
124 </html>

一个不敬业的前端攻城狮

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原文地址：https://www.cnblogs.com/chaoming/p/3195965.html