javascript实现图片切换、自动走、鼠标移入会停止，移出继续走

要实现以上效果并不难，把功能分开一步一步来实现就变得简单了，录制动态图不流畅，看代码意会吧！
<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        * {margin:0; padding: 0}
        button {
             50px;
        }
        p {
            text-align: center;
        }
        .active {
            background-color: yellow;
        }
        #wrap {
            210px;
            overflow: hidden;
            margin:0 auto;
        }
        #inner {
            9999px;
            overflow: hidden;
            position: relative;
            left:0;
            transition: left 0.6s;
        }
        #inner a {
            float: left;
        }
        #inner img {
            display: block;
            210px;
        }
    </style>

</head>
<body>
    
    <div id="wrap">
        <div id="inner">
            <a href="###"><img src="img/1.jpg"></a>
            <a href="###"><img src="img/2.jpg"></a>
            <a href="###"><img src="img/3.jpg"></a>
            <a href="###"><img src="img/4.jpg"></a>
            <a href="###"><img src="img/5.jpg"></a>
            <a href="###"><img src="img/6.jpg"></a>
            <a href="###"><img src="img/7.jpg"></a>
            <a href="###"><img src="img/8.jpg"></a>
            <a href="###"><img src="img/9.jpg"></a>
            <a href="###"><img src="img/10.jpg"></a>
            <a href="###"><img src="img/11.jpg"></a>
            <a href="###"><img src="img/12.jpg"></a>
            <a href="###"><img src="img/13.jpg"></a>
            <a href="###"><img src="img/14.jpg"></a>
        </div>
    </div>
    <p>
        <button class="active">1</button>
        <button>2</button>
        <button>3</button>
        <button>4</button>
        <button>5</button>
        <button>6</button>
        <button>7</button>
        <button>8</button>
        <button>9</button>
        <button>10</button>
        <button>11</button>
        <button>12</button>
        <button>13</button>
        <button>14</button>
    </p>
    <script type="text/javascript">
    //1.找节点
    var buttonList = document.getElementsByTagName("button");
    var inner = document.getElementById("inner");
    var perWidth = inner.children[0].offsetWidth;
    
    function tab() {
        inner.style.left = - perWidth * index + "px";
        for(var j = 0; j < buttonList.length; j++) {
            buttonList[j].className = "";
        }
        buttonList[index].className = "active";
    }
    for(var i = 0; i < buttonList.length; i++) {
        buttonList[i].index = i;
        buttonList[i].onclick = function() {
            index = this.index;
            tab();
        }
    }
    var index = 0;
    function next() {
        index ++;
        if(index > buttonList.length - 1) {
            index = 0;
        }
        tab();
    }
    var timer = setInterval(next,1000);

    inner.onmouseover = function() {
        // alert("鼠标移入");
        clearInterval(timer);
    }
    inner.onmouseout = function() {
        timer = setInterval(next,1000);
    }
    </script>
</body>
</html>
以后还会继续添加些效果补充完整的....