JavaScript 焦点轮播实现：无缝滚动与图片滑动切换技巧

<!DOCTYPE html>
<html>
<head lang="en">
  <meta charset="UTF-8">
  <title></title>
  <style type="text/css">
    *{
      margin: 0;
      padding: 0;
      list-style: none;
      text-decoration: none;
    }
    .wrap{
      width: 490px;
      height: 170px;
      margin: 100px auto;
      border: 1px solid #000000;
      position: relative;
      overflow: hidden;
    }
    #pic{
      width: 3430px;
      position: absolute;
    }
    #pic li{
      float: left;
      height: 170px;
    }
    #list{
      position: absolute;
      bottom: 10px;
      left:150px ;
    }
    #list li{
      float: left;
      width: 15px;
      height: 15px;
      background: #fff;
      margin: 0 10px;
      border-radius: 50%;
      cursor: pointer;
    }
    #list .on{
      background: #e27a00;
    }
    .Prev{
      top: 30px;
      left: 0;
    }
    .Next{
      top: 30px;
      right: 0;
    }
    .Prev,.Next{
      position: absolute;
      font-size: 80px;
      font-weight: bold;
      color:#fff ;
      -webkit-transition: all 0.35s ease-in-out
    }
    .Next:hover,
    .Prev:hover{
      background: #ccc;
      background: rgba(204, 204, 204, 0.4);
    }

  </style>
  <script type="text/javascript">
    window.onload=function(){
      var wrap=document.getElementById('wrap');
      var pic=document.getElementById('pic');
      var Li=document.getElementById('list').getElementsByTagName('li');
      var prev=document.getElementById('Prev');
      var next=document.getElementById('Next');
      var animated=false;
      var index=0;
      var timer=null;
      next.onclick=function(){
        if(animated){//如果图片正在滚动时要返回，否则index会变化
          return;
        }
        else{
          index++;
          if(index>=Li.length){
            index=0;
          }
        }

        showlist();
        if(animated == false){//if(!animated)
          animate(-490);
        }
      }
      prev.onclick=function(){
        if(animated){
          return;
        }
        else{
          index--;
          if(index<=0){
            index=Li.length-1;
          }
        }

        showlist();
        if(!animated){//判断其是否滚动完
          animate(490);
        }
      }
      for(var i=0;i<Li.length;i++){
        Li[i].num=i;
        Li[i].onclick=function(){
          if(this.className=="on"){
            return;
          }
          var offset = -490*(this.num-index);
          if(!animated){
            animate(offset);
          }
          index=this.num;
          showlist();
        }
      }
      //图片变换
      function animate(offset){
        animated=true;
        var newLeft=parseInt(pic.style.left) + offset;
        var time=300//位移总时间
        var interval=10;//位移间隔时间
        var speed=offset/(time/interval);//每次位移量

        function go(){
          if((speed < 0 && parseInt(pic.style.left) > newLeft )|| (speed > 0 && parseInt(pic.style.left) < newLeft)){
            pic.style.left = parseInt(pic.style.left) + speed + 'px';
            setTimeout(go,interval);
          }else{
            animated=false;
            pic.style.left= newLeft + 'px';
            if(newLeft > -490){
              pic.style.left = -2450 + 'px';
            }
            if(newLeft < -2450){
              pic.style.left = -490 + 'px';
            }
          }
        }
        go();
      }
      //圆点变换
      function showlist(){
        for(var i=0;i<Li.length;i++){
          Li[i].className="";
        }
        Li[index].className="on";
      }
      //自动播放
      function play(){
        timer=setInterval(function(){
          next.onclick();
        },2000);
      }
      function stop(){
        clearInterval(timer);
      }
      wrap.onmouseover=stop;
      wrap.onmouseout=play;
      play();
    }
  </script>
</head>
<body>
<div class="wrap" id="wrap">
  <ul id="pic" style="left: -490px;">
    <li><a href="#"><img src="/54111d7d00018ba604900170.jpg" alt="5"/></a></li>
    <li><a href="#"><img src="/54111cd9000174cd04900170.jpg" alt="1"/></a></li>
    <li><a href="#"><img src="/54111dac000118af04900170.jpg" alt="2"/></a></li>
    <li><a href="#"><img src="/54111d9c0001998204900170.jpg" alt="3"/></a></li>
    <li><a href="#"><img src="/54111d8a0001f41704900170.jpg" alt="4"/></a></li>
    <li><a href="#"><img src="/54111d7d00018ba604900170.jpg" alt="5"/></a></li>
    <li><a href="#"><img src="/54111cd9000174cd04900170.jpg" alt="1"/></a></li>
  </ul>
  <ul id="list">
    <li class="on"></li>
    <li></li>
    <li></li>
    <li></li>
    <li></li>
  </ul>
  <a href="javascript:;" class="Prev" id="Prev">&lt;</a>
  <a href="javascript:;" class="Next" id="Next">&gt;</a>
</div>
</body>
</html>