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

Uncaught TypeError: Cannot read property 'currentStyle' of undefined"

<!DOCTYPE html>
<html>
   <head>
       <meta charset="UTF-8">
       <title></title>
       <style>
*{
   margin: 0;
   padding: 0;
}
#div1{
   width:200px;
   height: 100px;
   background: yellow;
   margin-top: 10px;
   border:5px solid black;
   font-size: 12px;
   filter:alpha(opacity=30);
   opacity: 0.3;
}
       </style>
       <script>
           window.onload = function(){
               var div1=document.getElementById("div1");
               div1.onmouseover=function(){
                   move(this,"width",400);
               }
               div1.onmouseout=function(){
                   move(this,"width",200);
               }
           }
           var timer=null;
           function move(obj,attr,target){
               clearInterval(timer);
               timer=setInterval(function(){
                  var icur =0;
                  if (attr = "opacity") {
                          icur = Math.round(parseFloat(getstyle(obj.attr))*100);
                  } else{
                      var icur = parseInt(getstyle(obj,attr));
                  }

                   var speed =(target-icur)/8;
                       speed =speed>0?Math.ceil(speed):Math.floor(speed);
                   if(target==icur){
                       clearInterval(timer);
                   }else{
                   if (attr = "opacity") {
                       obj.style.filter ="alpha(opacity:"+(icur+speed)+")"
                           obj.style.opacity = (icur+speed)/100;
                       } else{
                           obj.style[attr] = icur+speed+"px";
                       }
                   }
               },30)
           }
       function getstyle(obj,attr){
           if(obj.currentStyle){
               return obj.currentStyle[attr];
           }else{
               return getComputedStyle(obj,false)[attr];
           }
       }
   </script>
   </head>
   <body>
       <div id="div1" >font-size</div>
   </body>
</html>

一直报错：Uncaught TypeError: Cannot read property 'currentStyle' of undefined"