原生JavaScript实现的无缝滚动功能详解

<div class="box" id="box">
  <ul class="J_XSlide list">
    <li class="J_tabContent"><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="img/main/display/1.jpg" alt="广告一" /></a></li>
    <li class="J_tabContent"><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="img/main/display/2.jpg" alt="广告一" /></a></li>
    <li class="J_tabContent"><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="img/main/display/3.jpg" alt="广告二" /></a></li>
    <li class="J_tabContent"><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="img/main/display/4.jpg" alt="广告三" /></a></li>
    <li class="J_tabContent"><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="img/main/display/5.jpg" alt="广告四" /></a></li>
    <li class="J_tabContent"><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="img/main/display/6.jpg" alt="广告五" /></a></li>
    <li class="J_tabContent"><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="img/main/display/1.jpg" alt="广告一" /></a></li>
  </ul>
  <div class="btn btnl"><</div>
  <div class="btn btnr">></div>
  <ul class="tabs">
    <li class="tab cur"></li>
    <li class="tab"></li>
    <li class="tab"></li>
    <li class="tab"></li>
    <li class="tab"></li>
    <li class="tab"></li>
  </ul>
</div>

<style>
   {
    margin: 0;
    padding: 0;
  }
  ul li {
    list-style: none;
  }
  .clearfix {
    zoom: 1;
  }
  .clearfix:after {
    display: block;
    clear: both;
    content: '';
  }
  .box {
    width: 1226px;
    height: 460px;
    overflow: hidden;
    position: relative;
    margin: 20px auto 0;
  }
  .box .list {
    position: relative;
    left: 0;
    height: 460px;
  }
  .box .list li img,
  .box .list li {
    float: left;
    width: 1226px;
    height: 460px;
  }
  .box .tabs {
    position: absolute;
    right: 5px;
    bottom: 5px;
    z-index: 99999;
   }
  .box .tabs .tab {
    float: left;
    width: 6px;
    height: 6px;
    border: 2px solid #f47500;
    border-radius: 100%;
    margin-right: 10px;
    cursor: pointer;
    background: #fcf2cf;
    font-family: arial;
  }
  .box .tabs .tab:hover,
  .box .tabs .cur {
    border: 2px solid #1227e4;
    background: #26c776;
  }
  .box .btn {
    position: absolute;
    width: 30px;
    height: 70px;
    : 50%;
    margin-: -35px;
    z-index: 20;
    background-color: rgba(0, 0, 0, 0.2);
    font-size: 30px;
    color: #fff;
    text-align: center;
    line-height: 70px;
  }
  .box:hover .btn {
    background-color: rgba(0, 0, 0, 0.6);
  }
  .box .btnl {
    left: 10px;
  }
  .box .btnr {
    right: 10px;
  }
</style>

  var GLOBAL = {};
  // 定义命名空间函数
  GLOBAL.namespace = function(str) {
    var arr = str.split("."),
      o = GLOBAL;
    for(i = (arr[0] === "GLOBAL") ? 1 : 0; i < arr.length; i++) {
      o[arr[i]] = o[arr[i]] || {};
      o = o[arr[i]];
    }
  };
  // Dom命名空间
  GLOBAL.namespace("Dom");
  // 获取className 第一个参数必须的（class名）、第二个参数父容器，缺省为body节点、第三个参数为DOM节点标签名
  GLOBAL.Dom.getElementsByClassName = function(str, root, tag) {
    if(root) {
      root = typeof root === 'string' ? document.getElementById(root) : root;
    }
    else {
      root = document.body;
    }
    tag = tag || '';
    var eles = root.getElementsByTagName(tag), // 获取父容器下所有标签
      arr = [];
    for(var i = 0, n = eles.length; i < n; i++) {
      for(var j = 0, k = eles[i].className.split(' '), l = k.length; j < l; j++) {
        if(k[j] == str) {
          arr.push(eles[i]);
          break;
        }
      }
    }
    return arr;
  };
  // Event命名空间
  GLOBAL.namespace('Event');
  // 添加事件（或者说监听事件）
  GLOBAL.Event.addHandler = function(node, eventType, handler) {
    node = typeof node === 'string' ? document.getElementById(node) : node;
    if(node.addEventListener) {
      node.addEventListener(eventType, handler, false);
    }
    else if(node.attachEvent) {
      node.attachEvent('on' + eventType, handler);
    }
    else {
      node['on' + eventType] = handler;
    }
  };

function getStyle(obj, attr) {
  return obj.currentStyle ? obj.currentStyle[attr] : getComputedStyle(obj, false)[attr];
}
function startMove(obj, json, fn) {
  clearInterval(obj.timer);
  obj.timer = setInterval(function() {
    var bS = true; //这一次运动结束——————所有值都到达了
    for(var attr in json) {
      //1.取当前的值
      var iCur = 0;
      if(attr == 'opacity') {
        var iCur = parseInt(parseFloat(getStyle(obj, attr))  100);
      }
      else {
        var iCur = parseInt(getStyle(obj, attr));
      }
      //2.计算速度
      var iSpeed = (json[attr] - iCur)/6;
      iSpeed = iSpeed>0?Math.ceil(iSpeed):Math.floor(iSpeed);
      //3.检测停止
      if(iCur != json[attr]) {
        bS = false;
      }
      if(attr == 'opacity') {
        obj.style.filter = 'alpha(opacity:' + (iCur + iSpeed) +')';
        obj.style.opacity = (iCur + iSpeed)/100;
      }
      else {
        obj.style[attr] = iCur + iSpeed + 'px';
      }
    }
    if(bS) {
      clearInterval(obj.timer);
      if(fn) {
        fn();
      }
    }
  }, 30);
}

  (function() {
    var oBox = document.getElementById('box');
    var oXSlide = GLOBAL.Dom.getElementsByClassName('J_XSlide', oBox)[0];
    var li = oXSlide.getElementsByTagName('li');
    var liTabs = GLOBAL.Dom.getElementsByClassName('tabs', oBox)[0].getElementsByTagName('li');
    var iNow = 0;
    function tab() {
      var timer = null;
      var playTime = 3000;
      var btn = GLOBAL.Dom.getElementsByClassName('btn', oBox);
      oXSlide.style.width = li.length  li[0].offsetWidth + 'px';
      for(var i = 0, len = liTabs.length; i < len; i++) {
        liTabs[i].index = i;
        GLOBAL.Event.addHandler(liTabs[i], 'mouseover', function() {
          iNow = this.index;
          showItem(iNow);
        });
      }
      GLOBAL.Event.addHandler(btn[0], 'click', moveLeft);
      GLOBAL.Event.addHandler(btn[1], 'click', moveRight);
      timer = setInterval(autoPlay, playTime);
      function autoPlay() {
        moveRight();
      }
      GLOBAL.Event.addHandler(oBox, 'mouseover', function() {
        clearInterval(timer);
      });
      GLOBAL.Event.addHandler(oBox, 'mouseout', function() {
        timer = setInterval(autoPlay, playTime);
      });
    }
    // 选项卡
    function showItem(n) {
      for(var i = 0, len = liTabs.length; i < len; i++) {
        liTabs[i].className = 'tab';
      }
      if(n == liTabs.length) {
        liTabs[0].className = 'tab cur';
      }
      else {
        liTabs[n].className = 'tab cur';
      }
      startMove(oXSlide, {'left': -n  li[0].offsetWidth});
    }
    function moveLeft() {
      iNow--;
      if(iNow == -1) {
        oXSlide.style.left = -liTabs.length  li[0].offsetWidth + 'px';
        iNow = liTabs.length - 1;
      }
      showItem(iNow);
    }
    function moveRight() {
      iNow++;
      if(iNow == li.length) {
        oXSlide.style.left = 0;
        iNow = 1;
      }
      showItem(iNow);
    }
    tab();
  })();