Native js and jQuery implement fade-in and fade-out carousel effect

The example in this article introduces the key code for realizing the fade-in and fade-out carousel effect based on jQuery, and shares it with you for your reference. The specific content is as follows:
Basic principle: Position all pictures absolutely at the same position, set the transparency to 0, and then use jQuery's fade-in and fade-out to achieve the picture switching effect.
html code:

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>一个轮播</title>
<style>
 #scrollPlay{
 width: 730px;
 height: 336px;
 /*overflow: hidden;*/
 }
 #pre{
 position: absolute;
 margin-top: 150px;
 width:30px;
 height: 30px;
 background: #000;
 color:#fff;
 opacity: 0.7;
 text-align: center;
 line-height: 30px;
 font-size: 20px;
 z-index: 10;
 }
 img{
 opacity: 0;
 position: absolute;
 }
 #next{
 position: absolute;
 margin-left:700px;
 margin-top: 150px;
 width:30px;
 height: 30px;
 background: #000;
 color:#fff;
 opacity: 0.7;
 text-align: center;
 line-height: 30px;
 font-size: 20px;
 z-index: 10;
 }
 span{
 display: block;
 width: 15px;
 height: 15px;
 float: left;
 border: 1px solid #fff;


 }
 #buttons{

 position: absolute;
 background: #000;
 margin-top: 300px;
 margin-left: 300px;
 z-index: 10;

 }

 .onactive{
 background: green;
 }
</style>
<script src='jquery.js'></script>
<script src='index.js'></script>
</head>
<body>
 <div id='scrollPlay'>
 <div id='buttons'>
  <span index = 0 class='onactive'></span>
  <span index = 1></span>
  <span index = 2></span>
  <span index = 3></span>
  <span index = 4></span>

 </div>
 <div id='pre'>&lt</div>
 <div id='next'>&gt</div>
 <img src='images/1.jpg' alt='pics' style='opacity:1'>
 <img src='images/2.jpg' alt='pics'>
 <img src='images/3.jpg' alt='pics'>
 <img src='images/4.jpg' alt='pics'>
 <img src='images/5.jpg' alt='pics'>
 </div>
</body>
 
</html>

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JS:

$(function(){

 var index = 0;
 var flag = false; //用于判断是否处于动画状态
 //切换函数
 function move(offset){ 
 flag=true;
 //console.log(offset)
 $('img').eq(index).fadeOut('slow',function(){
  if(offset>0){
  if(index ==4){
   index=0; 
  }else{
   //console.log(index);
   index=index+offset;
   //console.log(index);
  }
  }
  if(offset<0){
  if(index==0){
  index=4;
  }else{
  index=index+offset
  }
  }
  $('img').eq(index).fadeTo('slow',1) //使用fadeIn不成功:$('img').eq(index).fadeIn('slow')
  showButton();
  flag=false;
 }); 
 }


 //点击切换上一张
 $('#pre').click(function(){
 if(flag==false){
  move(-1)
 }
 
 })

 //点击切换下一张
 $('#next').click(function(){
 if(flag==false){
  move(1)
 }
 })

 //点击按钮直接切换
 $('span').click(function(){
 if(flag==false){
  var i= $(this).attr('index')
  //console.log(i)
  //console.log(index)
  //console.log(i-index)
  move(i-index) 
  showButton();
 }
 
 })
 
 //高亮显示按钮
 function showButton(){
 if($('span').hasClass('onactive')){
  $('span').removeClass();
 }
 $('span').eq(index).addClass('onactive')
 }


 //自动播放
 var timer;

 function go(){
 timer = setInterval(function(){
  $('#next').trigger('click');
 },3000)
 }
 //鼠标悬停，清除自动播放
 $('#scrollPlay').mouseover(function(){
  clearInterval(timer)
 })

 //鼠标移开，开始自动播放
 $('#scrollPlay').mouseout(function(){
  go();
 })

 go(); 
})

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At the end of the article, I raised a small question for you, and I hope you can give me a solution.
There is no effect when using fadeIn to fade in. In the end, it can only be achieved by using fadeTo. What is the reason?
Let me share with you a small example: Native JS implements fade-in/fade-out effect (fadeIn/fadeOut/fadeTo)
The fade effect is often used in daily projects. Unfortunately, native JS does not have a similar method, and sometimes small pages are not worth introducing a jQuery library, so I wrote one myself. It is encapsulated and useful. Friends who have it can use it directly. There is also a method to set the transparency of elements in the code, which is set according to IE rules (0~100). If it is changed to the standard setting method (0.00~1.00), please consider floating when using it below. Point to express the difference accurately.
Parameter description:
Both fadeIn() and fadeOut() have three parameters. The first is the event, which is required; the second is the fade-in and fade-out speed, a positive integer, the size is weighed by yourself, and is optional; the third is the specified fade-in and fade-out point. Transparency value (similar to fadeTo() in jQuery), a positive integer value from 0 to 100, which is also an optional parameter.

<html> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> 
<title>原生JS实现淡入淡出效果</title> 
<style> 
/*demo css*/ 
#demo div.box {float:left;width:31%;margin:0 1%} 
#demo div.box h2{margin-bottom:10px} 
#demo div.box h2 input{padding:5px 8px;font-size:14px;font-weight:bolder} 
#demo div.box div{text-indent:10px; line-height:22px;border:2px solid #555;padding:0.5em;overflow:hidden} 
</style> 
<script> 
window.onload = function(){ 
 //底层共用 
 var iBase = { 
 Id: function(name){ 
  return document.getElementById(name); 
 }, 
 //设置元素透明度,透明度值按IE规则计,即0~100 
 SetOpacity: function(ev, v){ 
  ev.filters &#63; ev.style.filter = 'alpha(opacity=' + v + ')' : ev.style.opacity = v / 100; 
 } 
 } 
 //淡入效果(含淡入到指定透明度) 
 function fadeIn(elem, speed, opacity){ 
 /* 
  * 参数说明 
  * elem==>需要淡入的元素 
  * speed==>淡入速度,正整数(可选) 
  * opacity==>淡入到指定的透明度,0~100(可选) 
  */ 
 speedspeed = speed || 20; 
 opacityopacity = opacity || 100; 
 //显示元素,并将元素值为0透明度(不可见) 
 elem.style.display = 'block'; 
 iBase.SetOpacity(elem, 0); 
 //初始化透明度变化值为0 
 var val = 0; 
 //循环将透明值以5递增,即淡入效果 
 (function(){ 
  iBase.SetOpacity(elem, val); 
  val += 5; 
  if (val <= opacity) { 
  setTimeout(arguments.callee, speed) 
  } 
 })(); 
 } 
 
 //淡出效果(含淡出到指定透明度) 
 function fadeOut(elem, speed, opacity){ 
 /* 
  * 参数说明 
  * elem==>需要淡入的元素 
  * speed==>淡入速度,正整数(可选) 
  * opacity==>淡入到指定的透明度,0~100(可选) 
  */ 
 speedspeed = speed || 20; 
 opacityopacity = opacity || 0; 
 //初始化透明度变化值为0 
 var val = 100; 
 //循环将透明值以5递减,即淡出效果 
 (function(){ 
  iBase.SetOpacity(elem, val); 
  val -= 5; 
  if (val >= opacity) { 
  setTimeout(arguments.callee, speed); 
  }else if (val < 0) { 
  //元素透明度为0后隐藏元素 
  elem.style.display = 'none'; 
  } 
 })(); 
 } 
 
 
 var btns = iBase.Id('demo').getElementsByTagName('input'); 
 
 btns[0].onclick = function(){ 
 fadeIn(iBase.Id('fadeIn')); 
 } 
 btns[1].onclick = function(){ 
 fadeOut(iBase.Id('fadeOut'),40); 
 } 
 btns[2].onclick = function(){ 
 fadeOut(iBase.Id('fadeTo'), 20, 10); 
 } 
 
} 
</script> 
</head> 
<body> 
 
<!--DEMO start--> 
<div id="demo"> 
 <div class="box"> 
 <h2><input type="button" value="点击淡入" /></h2> 
 <div id="fadeIn" style="display:none"> 
  <p>脚本之家</p> 
  <p>www.jb51.net</p> 
 </div> 
 <p>脚本之家是国内专业的网站建设资源.</p> 
 </div> 
 
 <div class="box"> 
 <h2><input type="button" value="点击淡出" /></h2> 
 <div id="fadeOut"> 
  <p>脚本之家</p> 
  <p>www.jb51.net</p> 
 </div> 
 <p>脚本之家是国内专业的网站建设资源.</p> 
 </div> 
 
 <div class="box"> 
 <h2><input type="button" value="点击淡出至指定透明度" /></h2> 
 <div id="fadeTo"> 
  
 </div> 
 <p>脚本之家是国内专业的网站建设资源.</p> 
 </div> 
</div> 
<!--DEMO end--> 
 
</body> 
</html>

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The above is the entire content of this article. I hope it will be helpful for everyone to learn native js and jQuery to achieve the fade-in and fade-out carousel effect.

Native js and jQuery implement fade-in and fade-out carousel effect_jquery