纯js实现淘宝商城轮播图

需求：
　　循环无缝自动轮播3张图片，点击左右箭头可以手动切换图片，鼠标点击轮播图下面的小圆点会跳转到对应的第几张图片。鼠标放到轮播图的图片上时不再自动轮播，鼠标移开之后又继续轮播。
效果图：

下面是html代码：

    <div id="box">
        <div id="imgbox">
            <div><img src="img/tu1.jpg" alt="" /></div>
            <div><img src="img/tu2.jpg" alt="" /></div>
            <div><img src="img/tu3.jpg" alt="" /></div>
        </div>
        <div class="yuandian">
            <a href="#" class="xiaoyuan"></a>
            <a href="#" class="xiaoyuan"></a>
            <a href="#" class="xiaoyuan"></a>
        </div>
        <div id="jiantou">
            <span id="jt_left" class="jiant">&lt;</span>
            <span id="jt_right" class="jiant">&gt;</span>
        </div>
    </div>

css代码：

* {
    margin: 0;
    padding: 0;
}
#box {
    position: relative;
     520px;
    height: 280px;
    /*background-color: pink;*/
    margin:100px auto;
    overflow: hidden;
}
#imgbox {
    position: absolute;
    top: 0;
    left: 0;
     99999px;
    cursor: pointer;
    height: 100%;
}
#imgbox img {
    float: left;
}
.yuandian {
    position: absolute;
    left: 230px;
    bottom: 20px;
     60px;
    height: 15px;
    border-radius: 20px;
    background: rgba(255,255,255,.6);
}
.yuandian a {
    float: left;
     10px;
    height: 10px;
    border-radius: 10px;
    margin: 2px 0 0 7px;
    background-color: white;
}

#jt_left {
    left: 0;
    border-top-right-radius:2em;
    border-bottom-right-radius:2em;
}
#jt_left,
#jt_right {
    position: absolute;
    top: 140px;
     35px;
    height: 35px;
    line-height: 35px;
    cursor: pointer;
    font-size: 18px;
    text-align: center;
    background: rgba(255,255,255,.6);
}
#jt_right {
    right: 0;
    border-top-left-radius:2em;
    border-bottom-left-radius:2em;
}

js代码：

<script type="text/javascript">
    //    获取小圆点
    var xiaoyuan = document.getElementsByClassName("xiaoyuan");
    //    获取装图片的盒子
    var imgbox = document.getElementById("imgbox");
    //     获取左右箭头
    var jiantou = document.getElementsByClassName("jiant");
    //小圆点控制图片
    xiaoyuan[0].onclick = function () {
        imgbox.style.left = 0;
    }
    xiaoyuan[1].onclick = function () {
        imgbox.style.left = "-520px";
    }
    xiaoyuan[2].onclick = function () {
        imgbox.style.left = "-1040px";
    }
    //左箭头控制图片
    jiantou[0].onclick = function () {
        if (imgbox.offsetLeft == 0) {
            imgbox.style.left = "-1040px";
            console.log(imgbox.offsetLeft);
        } else {
            imgbox.style.left = imgbox.offsetLeft + 520 + "px";
        }
    }
    //右箭头控制图片
    jiantou[1].onclick = function () {
        if (imgbox.offsetLeft <= -1040) {
            console.log(imgbox.offsetLeft);
            imgbox.style.left = 0;
        } else {
            imgbox.style.left = imgbox.offsetLeft - 520 + "px";
        }
    }
    //定时器控制图片轮播
    var fun1 = function () {
        if (imgbox.offsetLeft <= -1040) {
            imgbox.style.left = 0;
        } else {
            imgbox.style.left = imgbox.offsetLeft - 520 + "px";
        }
    }
    var t = setInterval(fun1, 2500);//fun1是你的函数
    // 鼠标经过停止轮播
    imgbox.onmouseover = function () {
        clearInterval(t) //关闭定时器
    }
    // 鼠标离开开启定时器 
    imgbox.onmouseout = function () {
        t=setInterval(fun1,2500)//重新开始定时器
    }
</script>