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

完成（透明度动画）

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <style type="text/css">
        #div1{
            width:200px;
            height: 200px;
            background:red;
            filter:alpha(opacity:30);/*IE9支持*/
            opacity:0.3; /*支持css3的浏览器*/
        }
    </style>
    <title></title>
</head>
<body>
<div id="div1"></div>
</body>
<script type="text/javascript">
    window.onload=function(){
        var odiv = document.getElementById("div1");
        odiv.onmouseover= function(){
            startMove(100);
        };
        odiv.onmouseout= function(){
            startMove(30);
        }
    };
    var timer = null;
    var alpha = 30;
    function startMove(iTarget){
        clearInterval(timer);
        var odiv = document.getElementById("div1");
        var timer = setInterval(function(){
            var speed = 0;
            if(alpha>iTarget){
                speed =-10;
            }else{
                speed = 10;
            }
           if(alpha == iTarget){
               clearInterval(timer);
           }else{
               alpha+=speed;
               odiv.style.filter='alpha(opactiy:alpha)';
               odiv.style.opacity=alpha/100;
           }
        },30)
    }
</script>
</html>