JavaScript移动端轮播图实现：触摸事件与原理详解

完整代码实现

<!DOCTYPE html>
<html>
<head>
 <title>移动端轮播</title>
 <style type="text/css">
  * {
   margin: 0;
   padding: 0;
  }
  #box {
   width: 980px;
   overflow: hidden;
   position: relative;
   margin: 0 auto;
  }
  #box ul {
   width: 4900px;
   height: 100px;
   position: relative;
   transform: translateX(-980px);
   
  }
  #box ul li{
   width: 980px;
   height: 100px;
   float: left;
   list-style-type: none;
   text-align: center;
   color: #fff;
   line-height: 100px;
   font-size: 30px;
  }
 </style>
 <script type="text/javascript">
  window.onload = function() {
   var box = document.getElementById('box');
   var oUl = document.getElementsByTagName('ul')[0];
   var aLi = oUl.children;//这样就可以把所有li标签获取到了
   var iNow = 1;
   var x = -iNow*aLi[0].offsetWidth;//li标签的位置
   var bReady = true;
   oUl.addEventListener('touchstart',function(ev){

    //当手指触摸屏幕的时候触发事件，让li的位置随手指滑动而改变
    if(bReady == false){return;}
    bReady = false; 
      
    var downX = ev.targetTouches[0].pageX; //记录触摸位置 
    var disX = downX - x;//下一个li要移动到的位置
    function fnMove(ev) {
     x = downX-disX;
     oUl.style.transform = 'translate3d('+x+'px,0,0)';
    }
    function fnEnd(ev){
     var upX = ev.changedTouches[0].pageX;//离开的位置
     if(Math.abs(upX - downX)>50){
      //左边移动
      if(upX - downX<0){
       iNow++;
       if(iNow==aLi.length){iNow=aLi.length-1;}
      }else{
      //右边移动
       iNow--;
       if(iNow==-1){iNow=0;}
      }
     }
     x = -iNow*aLi[0].offsetWidth;
     oUl.style.transform = 'translate3d('+x+'px,0,0)';
     oUl.style.transition = '200ms all ease';
     function tEnd(){
      if(iNow==4){
       iNow=1;
      }
      if(iNow==0){iNow=3;}
      oUl.style.transition = 'none'
      x = -iNow*aLi[0].offsetWidth;
      oUl.style.transform = 'translate3d('+x+'px,0,0)';
      bReady = true;
     } 
     oUl.addEventListener('transitionend',tEnd,false);
     //释放内存
     document.removeEventListener('touchend',fnEnd,false);
     document.removeEventListener('touchmove',fnMove,false);

    }
    document.addEventListener('touchmove',fnMove,false);
    document.addEventListener('touchend',fnEnd,false);
    //阻止默认事件
    ev.preventDefault();
   },false);

  }
 </script>
</head>
<body>
 <div id="box"> 
 <ul>
  <li style="background:green">3</li>
  <li style="background:orange">1</li>
  <li style="background:yellow">2</li>
  <li style="background:green">3</li>
  <li style="background:orange">1</li>
 </ul>
 </div> 
</body>
</html>