原生js焦点轮播图主要注意这几点：
1、前后按钮实现切换，同时注意辅助图
2、中间的button随着前后按钮对应切换，同时按button也能跳转到相应的index
3、间隔调用与无限轮播。
4、注意在动画时要停止按钮，或者说上一个动画完毕下一个动画才能执行
5、另外在切换图片的时候，底部的Button动画效果，是从底部开始往上升的，要用到transform:scale()和transform-origin:0 100%两个转换属性，代码如下
<!DOCTYPE html> <html> <head> <meta charset="utf-8"/> <meta content="width=device-width,initial-scale=1,user-scalable="no"> <title>20170101</title> <style type="text/css"> a{text-decoration:none;color:#3DBBF5;} .wrapper{width:750px;height:350px;background:#001032;margin:20px auto;text-align:center;box-shadow:0 0 12px 2px hsla(0,20%,30%,0.5);padding:10px 15px;position:relative;} .effect{position:relative;cursor:pointer;} .effect:hover{color:#02a0e9;} .effect:before{width:100%;display:inline-block !important;position:absolute;height:1px;background:#02a0e9;transition:all 0.4s ease-in-out;-webkit-transition:all 0.4s ease-in-out;-moz-transition:all 0.4s ease-in-out;transform:scale(0,1);content:'';bottom:-5px;left:0;} .effect:hover:before{transform:scale(1);-webkit-transform:scale(1);} #lunBo{margin-top:20px;overflow:hidden;height:300px;width:750px;position:relative;} #list{position:absolute;z-index:22;height:300px;width:5250px;} #list img{float:left;} #buttons { position: absolute; height: 20px; width: 150px; z-index: 99; bottom: 20px; left: 40%;} span { cursor: pointer; float: left; width: 10px; height: 5px; background: #333; margin-right: 10px;} .on { background: yellow;transition:all 0.4s ease-in-out;-webkit-transition:all 0.4s ease-in-out;-moz-transition:all 0.4s ease-in-out;transform:scale(1,4);-ms-transform:scale(1,4);-moz-transform:scale(1,4);-webkit-transform:scale(1,4);transform-origin:0% 0%;-webkit-transform-origin:0% 100%;-moz-transform-origin:0% 100%;} .arrow { cursor: pointer; display: none; line-height: 39px; text-align: center; font-size: 36px; font-weight: bold; width: 40px; height: 100px; line-height:100px;position: absolute; z-index: 92; top: 30%; background-color: RGBA(0,0,0,.3); color: #fff;} .arrow:hover { background-color: RGBA(0,0,0,.7);} #lunBo:hover .arrow { display: block;} #prev { left: 0px;} #next { right: 0px;} </style> </head> <body> <div> <a href="#">2016完了,2017来了</a> <div> <div> <img src="https://cdn.attach.qdfuns.com/notes/pics/201701/03/175856saeagzgsnwal15n5.jpg" alt=""/> <img src="https://cdn.attach.qdfuns.com/notes/pics/201701/02/235009drzwcaxem2wfgmdc.jpg" alt=""/> <img src="https://cdn.attach.qdfuns.com/notes/pics/201701/03/175856m1bhxxx1d8jfnblb.jpg" alt=""/> <img src="https://cdn.attach.qdfuns.com/notes/pics/201701/03/175856z48mfrrr8u064rf6.jpg" alt=""/> <img src="https://cdn.attach.qdfuns.com/notes/pics/201701/03/175856e95yze236lvq7y2a.jpg" alt=""/> <img src="https://cdn.attach.qdfuns.com/notes/pics/201701/03/175856saeagzgsnwal15n5.jpg" alt=""/> <img src="https://cdn.attach.qdfuns.com/notes/pics/201701/02/235009drzwcaxem2wfgmdc.jpg" alt=""/> </div> <div> <span index="1"></span> <span index="2"></span> <span index="3"></span> <span index="4"></span> <span index="5"></span> </div> <a href="javascript:;"><</a> <a href="javascript:;">></a> </div> </div> <script> window.onload = function(){ var lunBo = document.getElementById('lunBo'); var list = document.getElementById('list'); var buttons = document.getElementById('buttons').getElementsByTagName('span'); //console.log(buttons); var prev = document.getElementById('prev'); var next = document.getElementById('next'); var index = 1; var animated = false; var interval = 3000; var timer; //显示按钮的索引 function showButton(){ for(var i = 0 ; i < buttons.length ; i++){ if( buttons[i].className == 'on' ){ buttons[i].className = ''; break; }; }; buttons[index - 1].className='on'; }; function play(){ timer = setTimeout(function () { next.onclick(); play(); }, interval); }; function stop(){ clearTimeout(timer); }; //向前按钮 next.onclick = function () { if (animated) { return; } if (index == 5) { index = 1; } else { index += 1; } animate(-750); showButton(); }; prev.onclick = function () { if (animated) { return; } if (index == 1) { index = 5; } else { index -= 1; } animate(750); showButton(); }; //parseInt()转换为纯数值 function animate(offset){ animated = true; var newLeft = parseInt(list.style.left) + offset; //目标值 var time = 300; //位移总时间为300 var interval = 10; // var speed = offset/(Math.floor(time/interval)); //每次位移量 function go(){ if( (speed < 0 && parseInt(list.style.left) > newLeft) || ( speed > 0 && parseInt(list.style.left) < newLeft) ){ list.style.left = parseInt(list.style.left) + speed + 'px'; setTimeout(go,interval); }else{ animated = false; list.style.left = newLeft+ 'px'; //现在的位移 if( newLeft > -750){ //假的辅助图 list.style.left = -3750 + 'px'; } if( newLeft < -3750){ list.style.left = -750 + 'px'; } } }; go(); }; //小按钮 for(var i=0;i < buttons.length;i++){ buttons[i].onclick = function(){ if(this.className == 'on'){ return; }; var myIndex = parseInt(this.getAttribute('index')); var offset = -750 * (myIndex - index); animate(offset); index = myIndex; showButton(); } } lunBo.onmouseout = play; lunBo.onmouseover = stop; play(); } </script> </body> </html>