JS按钮控制内容左右滚动

运行效果如下：
代码如下：
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>JS按钮控制内容左右滚动</title>
    <style>
    *{ padding: 0; margin: 0;}
    li{ list-style: none;}
    .clearfix{ *zoom:1;}
    .clearfix:after{ clear: both; display: block; content: ""; height: 0; overflow: hidden;}
    a{ text-decoration: none; color: #333;}
    a:hover{ color: #f00;}
    .center{ text-align: center; margin-top: 20px; font-family: "Microsoft Yahei";}
    #box{ width: 700px; margin: 20px auto; border: 1px solid #ccc; background: #fff; font-size: 12px; position: relative; height: 120px;}
    #left ,#right{ position: absolute; z-index: 2px; cursor: pointer; background: #eee; width: 20px; text-align: center; height: 100%; line-height: 2.4; }
    #left{ left: 0;}
    #right{ right: 0;}
    .content{ margin-left: 20px; width: 660px; height: 120px; overflow: hidden; position: relative; background: #ccc;}
    #wrap{ position: absolute; left: 0; width: 1500px;}
    #wrap ul{ padding: 10px 0;}
    #wrap li{ float: left; width: 120px; height: 100px; background: purple; margin-left: 10px;}
    </style>
</head>
<body>
    <h3 class="center">先向左滚动试试，然后向右滚动试试</h3>
    <div id="box">
        <a id="left" href="javascript:;">向左滚动</a>
        <a id="right" href="javascript:;">右下滚动</a>
        <div class="content">
            <div id="wrap">
                <ul class="clearfix">
                    <li>1</li>
                    <li>2</li>
                    <li>3</li>
                    <li>4</li>
                    <li>5</li>
                    <li>6</li>
                    <li>7</li>
                    <li>8</li>
                    <li>9</li>
                    <li>10</li>
                </ul>
            </div>
        </div>
    </div>
    <script>

    // 封装getStyle函数
    function getStyle(obj,attr){
        return obj.currentStyle ? obj.currentStyle[attr] : getComputedStyle(obj,false)[attr];
    }

    window.onload = function(){
        var oBox = document.getElementById('box');
        // alert(getStyle(oBox,'width'));        // 700px
        var oLeft = document.getElementById('left');
        var oRight = document.getElementById('right');
        var oWrap = document.getElementById('wrap');
        var num = 0;
        var timer = null;

        oLeft.onmousedown = function(){
            oWrap.timer = setInterval(function(){
                var dis = parseInt(getStyle(oWrap,'left')) - 5;
                if(dis < -650){
                    dis = -650;
                }
                oWrap.style.left = dis + 'px';
            },30);
        };

        oLeft.onmouseup = function(){
            clearInterval(oWrap.timer);
        };

        oRight.onmousedown = function(){
            oWrap.timer = setInterval(function(){
                var dis = parseInt(getStyle(oWrap,'left')) + 5;
                if(dis > 0){
                    dis = 0;
                }
                oWrap.style.left = dis + 'px';
            },30);
        };

        oRight.onmouseup = function(){
            clearInterval(oWrap.timer);
        };
    };
    /*function getStyle(obj ,attr){
        return obj.currentStyle ? obj.currentStyle[attr] :getComputedStyle(obj ,false)[attr];
    }

    window.onload = function(){
        var oBox = document.getElementById('box');
        // alert(getStyle(oBox,'width'))        // 168px
        var oUp = document.getElementById('up');
        var oDown = document.getElementById('down');
        var oWrap = document.getElementById('wrap');
        var num = 0;
        var timer = null;

        // 鼠标按下向上链接，开启定时器
        oUp.onmousedown = function(){
            oWrap.timer = setInterval(function(){
                // 先获取内容的top值[获取的是字符串，所以要用parseInt转换成数字]，然后让它每隔300ms减少5px使之向上运动
                var dis = parseInt(getStyle(oWrap,'top')) - 5;
                // 这里的200是根据当前案例设置的，可以根据实际情况调整数值
                if( dis < -220){
                    dis = -220;
                }
                oWrap.style.top = dis + 'px';
            },30);
        };

        // 鼠标移开向上链接，关闭定时器
        oUp.onmouseup = function(){
            clearInterval(oWrap.timer);
        };

        // 鼠标按下向下链接，开启定时器
        oDown.onmousedown = function(){
            oWrap.timer = setInterval(function(){
                var dis = parseInt(getStyle(oWrap,'top')) + 5;
                if(dis > 0){
                    dis = 0;
                }
                oWrap.style.top = dis + 'px';
            },30);
        };

        // 鼠标移开向下链接，关闭定时器
        oDown.onmouseup = function(){
            clearInterval(oWrap.timer);
        };
    };*/
    </script>
</body>
</html>