                        课程
                    
                        /前端开发
                        
                            /JavaScript
                        
                        /JS动画效果

为什么speed直接用小数不可以，只能用整数，speed/100才可以，用小数判断出错？？？？

<!DOCTYPE html>
<html>
   <head>
       <meta charset="UTF-8">
       <title></title>
   </head>
   <style type="text/css">
       #one{
           width:200px;
           height:200px;
           opacity: 0.3;
           background: red;
       }
   </style>
   <script type="text/javascript">
       window.onload=function(){
           var one=document.getElementById("one");
           one.onmouseover=function(){
               startMove(1);
           }
           one.onmouseout=function(){
               startMove(0.3);
           }
       }
       var timer=null;
       var alpha=0.3;
       function startMove(target){
       var one=document.getElementById("one");
       clearInterval(timer);
       var speed=0;
       if(alpha>target){
           speed=-0.1;
       }else{
           speed=0.1;
       }
       timer=setInterval(function(){
           if(alpha==target){
               clearInterval(timer);
           }
           else{
               alpha+=speed;
               one.style.opacity=alpha;
           }
       },30);

       }
   </script>
   <body>
       <div id="one"></div>
   </body>
</html>