javascript每日一练（十二）——运动框架

运动框架

　　可以实现多物体任意值运动
例子：
 <!doctype html>
 <html>
 <head>
 <meta charset="utf-8">
 <title>运动框架</title>
 <style>
 #div1{ width:100px; height:100px; background:red; position:absolute; left:0; top:50px; opacity:0.3; filter:alpha(opacity=30);}
 </style>
 <script>
 window.onload = function()
 {
     var oBtn = document.getElementById('btn1');
     var oDiv = document.getElementById('div1');

     oBtn.onclick = function()
     {
         startMove(oDiv, {width:200, height:200, opacity:100}, function(){
             startMove(oDiv, {width:100, height:100, opacity:30});
         });
     };
 };

 function getStyle(obj, attr)
 {
     if(obj.currentStyle){
         return obj.currentStyle[attr];
     }else{
         return getComputedStyle(obj, false)[attr];
     }
 }

 function startMove(obj, json, fn)
 {
     clearInterval(obj.timer);

     obj.timer = setInterval(function(){
         var bStop = true;
         for(var attr in json){
             var iCur = 0;

             if(attr == 'opacity'){
                 iCur = Math.round(parseFloat(getStyle(obj, attr))*100);
             }else{
                 iCur = parseInt(getStyle(obj, attr));
             }

             var iSpeed = (json[attr] - iCur)/8;
             iSpeed = iSpeed>0?Math.ceil(iSpeed):Math.floor(iSpeed);

             if(iCur != json[attr]){
                 bStop = false;
             }

             if(attr == 'opacity'){
                 obj.style.filter = 'alpha(opacity='+(iCur+iSpeed)+')';
                 obj.style.opacity = (iCur+iSpeed)/100;
             }else{
                 obj.style[attr] = iCur + iSpeed + 'px';
             }

         }

         if(bStop){
             clearInterval(obj.timer);
             if(fn){
                 fn();
             }
         }
     }, 30);
 }
 </script>
 </head>

 <body>
 <input id="btn1" type="button" value="运动"/>
 <div id="div1"></div>
 </body>
 </html>