JS动画效果——多物体动画@慕课网原创_慕课网

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>多物体动画</title>
</head>
<style>
    body,ul,li{
        margin: 0;
        padding: 0;
    }
    ul,li{
        list-style: none;
    }
    ul li{
        width: 150px;
        height: 150px;
        background: yellow;
        margin-bottom: 20px;
        border: 12px solid #000;
        font-size: 1px;
        color: #00f;
        filter: alpha(opacity: 30);
        opacity: 0.3;
    }
</style>
<script>
    window.onload = function () {
        var aLi = document.getElementsByTagName('li');
        for(var i = 0; i < aLi.length; i++){
            aLi[i].timer = null;
            if (Math.random()<0.333) {
                aLi[i].onmouseover = function () {
                    startMove(this, 'width', 300);
                };
                aLi[i].onmouseout = function () {
                    startMove(this, 'width', 150);
                }
            } else if (Math.random()<0.666) {
                aLi[i].onmouseover = function () {
                    startMove(this, 'height', 300);
                };
                aLi[i].onmouseout = function () {
                    startMove(this, 'height', 150);
                }
            } else {
                aLi[i].onmouseover = function () {
                    startMove(this, 'opacity', 100);
                };
                aLi[i].onmouseout = function () {
                    startMove(this, 'opacity', 30);
                }
            }
        }
    };

    var speed = 0;

    function startMove(obj, attr, iTarget) {
        clearInterval(obj.timer);
        obj.timer = setInterval(function () {
            var icur = 0;
            if (attr == 'opacity'){
                icur = Math.round(parseFloat(getStyle(obj,attr)) * 100);
            } else {
                icur = parseInt(getStyle(obj, attr));
            }
            speed = (iTarget - icur)/8;
            speed = speed > 0 ? Math.ceil(speed) : Math.floor(speed);
            if (icur == iTarget){
                clearInterval(obj.timer);
            }else{
                if (attr == 'opacity'){
                    obj.style.filter = 'alpha(opacity: '  + (icur + speed) + ');';
                    obj.style[attr] = (icur + speed)/100;
                } else {
                    obj.style[attr] = icur + speed + 'px';
                }
                obj.style.fontSize = parseInt(getStyle(obj, 'fontSize')) + speed+ 'px';
            }
        },30)
    }

    function getStyle(obj, attr){
        if (obj.currentStyle){
            return obj.currentStyle[attr];
        }else{
            return getComputedStyle(obj, false)[attr];
        }
    }
</script>
<body>
<ul>
    <li>font-size</li>
    <li>font-size</li>
    <li>font-size</li>
    <li>font-size</li>
    <li>font-size</li>
</ul>
</body>
</html>