练习：javascript淡入淡出半透明效果

时间：2022-07-18 22:47:32

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练习：javascript淡入淡出半透明效果

<!DOCTYPE html>

<html lang="en">

<head>

    <meta charset="UTF-8">

    <title>淡入淡出半透明效果</title>

    <style>

        img {width:400px;height:200px;opacity: 0.3;filter:alpha(opacity=30)}

    </style>

</head>

<body>

<img src="data:images/4.jpg" alt="" id="img">

<script>

    // opacity IE8及以下版本不支持

    var oImg= document.getElementById('img');

    oImg.onmouseover=function(){

        animate(30,100)

    }

    oImg.onmouseout=function(){

        animate(100,30)

    }

    var timer = null;

    function animate(speed,dest){

       //speed初始透明度，dest透明度目标值

        clearInterval(timer);

        timer = setInterval(function(){

            speed<dest?speed+=10:speed-=10;

            if(speed==dest){

                clearInterval(timer);

                timer=null;

            }else {

                oImg.style.opacity=speed/100;

                oImg.style.filter="alpha(opacity:"+speed+")";

            }

        },20)

    }

</script>

</body>

</html>

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