js实现自动轮播（原生js封装无缝轮播功能）

(function(window, undefined) {
 
 // 获取元素css属性值
 function getCss(elem, attr) {
  return elem.currentStyle ? 
   elem.currentStyle[attr] : 
   window.getComputedStyle(elem, null)[attr];
 }
 
 // 去除字符串中的非数字，不包括负号
 function toInt(str) {
  var rex = /[^0-9]/ig;
  return Number((str[0] === '-' && str[1] !== '=') ? '-' + str.replace(rex, '') : str.replace(rex, ''));
 }
 
 // 封装动画函数，参数：dom对象、css属性值对象、动画执行时间、动画完成后回调
 function animation(elem, params, speed, callback) {
  for (var param in params) {
   (function(param) {
    
    var elemValue = toInt(getCss(elem, param)),
     targetValue = toInt(params[param]),
     currentDis = elemValue,
     unit = params[param].substr(params[param].indexOf('[A-Za-z]+') - 1);
    
    if (params[param].length > 2) {
     var prefix = params[param].substr(0, 2);
     
     if (prefix === '+=')
      targetValue = elemValue + targetValue;
     else if (prefix === '-=')
      targetValue = elemValue - targetValue;
    }
    
    var dis = (targetValue - elemValue) / speed,
     sizeFlag = targetValue < elemValue;
    
    var timer = setInterval(function() {
     
     elemValue = toInt(getCss(elem, param));
     
     if (sizeFlag) {
      if (currentDis <= targetValue) {
       clearInterval(timer);
       elem.style[param] = targetValue + unit;
      } else {
       currentDis += dis;
       elem.style[param] = currentDis + unit;
      }
     }
     else {
      if (currentDis >= targetValue) {
       clearInterval(timer);
       elem.style[param] = targetValue + unit;
      } else {
       currentDis += dis;
       elem.style[param] = currentDis + unit;
      }
     }
    }, 1);
    
   })(param);
  }
  
  if (typeof callback === 'function')
   callback();
 };
 
 
 // 向右轮播数组移动
 function rightRoundArrayMove() {
  
  var winsLen = wins.length;
  var lastWin = wins[winsLen - 1];
  
  for (var i = winsLen - 1; i > 0; i--) 
   wins[i] = wins[i - 1];
  
  wins[0] = lastWin;
 }
 
 // 向左轮播
 function rightRound(time) {
  
  rightRoundArrayMove();
  
  wins.forEach(function(win, index) {
   (index === 0) ? 
    win.style.left = index * winWidth - winWidth + 'px' :
    animation(win, {left: '+=' + winWidth + 'px'}, time ? time : animationTime);
  });
 }
 
 // 向右轮播
 function leftRound(time) {
  
  var winsLen = wins.length;
  var firstWin = wins[0];
  
  for (var i = 0; i < winsLen - 1; i++)
   wins[i] = wins[i + 1];
   
  wins[winsLen - 1] = firstWin;
  
  wins.forEach(function(win, index) {
   (index === wins.length - 1) ? 
    win.style.left = index * winWidth - winWidth + 'px' :
    animation(win, {left: '-=' + winWidth + 'px'}, time ? time : animationTime);
  });
 }
 
 
 var 
  // wins, btns, sbtns用于保存构造函数的参数
  wins, 
  btns, 
  sbtns, 
  // 窗口的宽度
  winWidth,
  // 过渡动画时间(毫秒)，默认为100
  animationTime = 100,
  // 点击按钮轮播间隔
  clickInterval = animationTime << 2,
  // 保存自动轮播定时器、定时器间隔、是否向右轮播
  autoRoundTimer,
  qinterval,
  qisRight,
  // slide构造函数，参数：窗口数组，按钮数组，侧边按钮数组
  slide = function(wins, btns, sbtns) {
   return new slide.prototype.init(wins, btns, sbtns);
  };
  
 
 slide.prototype = {
  
  // 初始化窗口元素
  init: function(awins, abtns, asbtns) {
   
   if (!awins)
    throw new Error('The window array cannot be empty.');
   
   wins = Object.values(awins), btns = abtns, sbtns = asbtns;
   
   // 处理窗口少于3个的情况
   if (wins.length === 1) {
    var winParent = wins[0].parentNode;
    var winHTML = wins[0].outerHTML;
    winParent.innerHTML += winHTML + winHTML;
    wins = Object.values(winParent.children);
   }
   else if (wins.length === 2) {
    var winParent = wins[0].parentNode;
    winParent.innerHTML += wins[0].outerHTML + wins[1].outerHTML;
    wins = Object.values(winParent.children);
   }
   
   winWidth = wins[0].offsetWidth;
   
   wins.forEach(function(win, index) {
    win.style.position = 'absolute';
    win.index = index;
   });
   
   rightRoundArrayMove();
   
   wins.forEach(function(win, index) {
    win.style.left = index * winWidth - winWidth + 'px';
   });
  },
  
  // 设置过渡动画时间
  setAnimationTime: function(time) {
   animationTime = time;
   clickInterval = animationTime << 2;
  },
  
  // 自动轮播，参数：轮播时间间隔、是否为向右轮播
  autoRound: function(interval, isRight) {
   autoRoundTimer = setInterval(function() {
        isRight ? rightRound() : leftRound();
       }, interval);
   qinterval = interval;
   qisRight = isRight;
  },
  
  // 侧边按钮点击，参数为侧边按钮元素数组，该参数可在构造函数中传递或现在传递
  sideBtnClickRound: function(sabtns) {
   
   var leftBtn = sabtns ? sabtns[0] : sbtns[0],
    rightBtn = sabtns ? sabtns[1] : sbtns[1];
   
   var isclick= true;
   leftBtn.onclick = function () {
    if(isclick) {
     isclick= false;
     rightRound();
     setTimeout(function() { 
      isclick = true;
     }, clickInterval);
    }
   };
   
   rightBtn.onclick = function () {
    if(isclick) {
     isclick= false;
     leftRound();
     setTimeout(function() {
      isclick = true;
     }, clickInterval);
    }
   };
  },
  
  // 普通按钮点击，参数：普通按钮数组、回调
  btnsClickRound: function(abtns, callback) {
   
   var ibtns = abtns ? abtns : btns;
   
   var isclick= true;
   
   ibtns.forEach(function(btn, index) {
    btn.onclick = function() {
     if(isclick) {
      isclick= false;
      
      if (typeof callback === 'function')
       callback(ibtns, btn, index);
      
      var poor = index - wins[1].index;
      var count = Math.abs(poor);
      if (poor < 0) {
       var absPoor = count;
       var timer = setInterval(function() {
        console.log((absPoor + 1))
           rightRound(animationTime / (absPoor + 2));
           if ((--count) === 0) 
            clearInterval(timer);
          }, animationTime);
      }
      else if (poor > 0) {
       var timer = setInterval(function() {
           leftRound(animationTime / (poor + 2));
           if ((--count) === 0) 
            clearInterval(timer);
          }, animationTime);
      }
      
      setTimeout(function() {
       isclick = true;
      }, clickInterval << 1);
     }
    }
   });
  },
  
  // 设置鼠标移入取消自动轮播，参数：移入的元素、移入元素回调、移出元素回调
  setOverStop: function(box, overCallback, outCallback) {
   box.onmouseover = function(e) {
    clearInterval(autoRoundTimer);
    
    if (typeof overCallback === 'function')
     overCallback(e);
   }
   box.onmouseout = function(e) {
    slide.prototype.autoRound(qinterval, qisRight);
    
    if (typeof outCallback === 'function')
     outCallback(e);
   }
  }
 }
 
 slide.prototype.init.prototype = slide.prototype;
 window.slide = _slide = slide;
 
})(window);

onload = function() {
 
 var wins = document.querySelectorAll('.wins > li');
 var btns = document.querySelectorAll('.btns > li');
 var sideBtns = document.querySelectorAll('.side-btns > li');
 var box = document.querySelector('.box');
 
 var s = slide(wins, btns, sideBtns); // 创建轮播对象，参数：窗口dom数组、下方按钮dom数组（可选）、
 s.autoRound(2000);   // 设置自动轮播
 s.setAnimationTime(200); // 设置过渡动画时间
 s.setOverStop(box);   // 设置鼠标移入元素时自动轮播停止，参数：移入的dom元素、移入元素回调、移出元素回调
 s.sideBtnClickRound();  // 设置点击侧边按钮时轮播，参数：按钮dom数组（可选）
 s.btnsClickRound();   // 设置下方按钮点击时轮播，参数：按钮dom数组（可选）、回调
}

<!DOCTYPE html>
<html>
 <head>
  <meta charset="utf-8" />
  <title></title>
  <style type="text/css">
   * {
    margin: 0;
    padding: 0;
   }
   
   li {
    list-style: none;
   }
   
   .box {
    width: 1000px;
    height: 400px;
    margin: 20px auto;
    display: flex;
    align-items: center;
    position: relative;
    overflow: hidden;
   }
   
   .box > * {
    position: absolute;
   }
   
   .side-btns {
    width: inherit;
    height: 100px;
    display: flex;
    justify-content: space-between;
    z-index: 2;
   }
   
   .side-btns > li {
    width: 50px;
    height: inherit;
    text-align: center;
    line-height: 100px;
    font-size: 18px;
    background-color: rgba(0, 0, 0, .3);
    color: white;
    cursor: pointer;
    user-select: none;
   }
   
   .btns {
    width: inherit;
    height: 20px;
    display: flex;
    justify-content: flex-end;
    z-index: 2;
    position: absolute;
    bottom: 20px;
   }
   
   .btns > li {
    width: 16px;
    height: 16px;
    border-radius: 50%;
    margin-right: 12px;
    cursor: pointer;
    background-color: rgba(0, 0, 0, .2);
   }
   
   .wins {
    width: inherit;
    height: inherit;
    display: flex;
   }
   
   .wins > li {
    width: inherit;
    height: inherit;
    flex-grow:0;
    flex-shrink:0;
   }
  </style>
  <script src="js/slide.js"></script>
  <script src="js/test.js"></script>
 </head>
 
 <body>
  <li class="box">
   <li class="side-btns">
    <li class="left-btn">&lt;</li>
    <li class="right-btn">&gt;</li>
   </li>
   
   <ul class="btns">
    <li></li>
    <li></li>
    <li></li>
    <li></li>
   </ul>
   
   <ul class="wins">
    <li style="background-color: antiquewhite;">a</li>
    <li style="background-color: aquamarine;">b</li>
    <li style="background-color: green;">c</li>
    <li style="background-color: brown;">d</li>
   </ul>
  </li>
 </body>
</html>