轮播图加入定时器

<!DOCTYPE html>
<html lang="zh-CN">
<head>
  <meta charset="UTF-8">
  <title>京东商城</title>
  <style>
    * {
      margin: 0;
      padding: 0;
      list-style: none;
    }
    
    .slider {
      height: 340px;
       790px;
      margin: 100px auto;
      position: relative;
    }
    
    .slider li {
      position: absolute;
      display: none;
    }
    
    .slider li:first-child {
      display: block;
    }
    
    .arrow {
      display: none;
    }
    
    .slider:hover .arrow {
      display: block;
    }
    
    .arrow-left,
    .arrow-right {
      font-family: "SimSun", "宋体";
       30px;
      height: 60px;
      background-color: rgba(0, 0, 0, 0.1);
      position: absolute;
      top: 50%;
      margin-top: -30px;
      cursor: pointer;
      text-align: center;
      line-height: 60px;
      color: #fff;
      font-weight: 700;
      font-size: 30px;
    }
    
    .arrow-left:hover,
    .arrow-right:hover {
      background-color: rgba(0, 0, 0, .5);
    }
    
    .arrow-left {
      left: 0;
    }
    
    .arrow-right {
      right: 0;
    }
  
  </style>
</head>
<body>
<div class="slider">
  <ul>
    <li><a href="#"><img src="images/1.jpg" alt=""></a></li>
    <li><a href="#"><img src="images/2.jpg" alt=""></a></li>
    <li><a href="#"><img src="images/3.jpg" alt=""></a></li>
    <li><a href="#"><img src="images/4.jpg" alt=""></a></li>
    <li><a href="#"><img src="images/5.jpg" alt=""></a></li>
    <li><a href="#"><img src="images/6.jpg" alt=""></a></li>
    <li><a href="#"><img src="images/7.jpg" alt=""></a></li>
    <li><a href="#"><img src="images/8.jpg" alt=""></a></li>
  </ul>
  <!--箭头-->
  <div class="arrow">
    <span class="arrow-left">&lt;</span>
    <span class="arrow-right">&gt;</span>
  </div>
</div>

<script src="jquery-1.12.4.js"></script>
<script>
  $(function () {
    var $li = $(".slider>ul>li");
    var count = 0;
    var timer =null;
    var interval =1000 ;
    
    $(".arrow-right").click(function () {
      count++;
      if(count == $li.length){
        count = 0;
      }
      $li.eq(count).fadeIn(1000).siblings().fadeOut(1000);
    });
  
    $(".arrow-left").click(function () {
      count--;
      if(count == -1){
        count = $li.length - 1;
      }
      $li.eq(count).fadeIn(1000).siblings().fadeOut(1000);
    });

    timer=setInterval(function () {
      $(".arrow-right").trigger("click");
    },interval);

    $(".slider").mouseenter(function () {
      clearInterval(timer);
    });
    $(".slider").mouseleave(function () {
      timer=setInterval(function () {
        $(".arrow-right").trigger("click");
      },interval);
    });


  })
</script>
</body>
</html>
效果：
自动轮播，当鼠标进入该区域的时候停止轮播，当鼠标离开的时候执行自动轮播