Use jQuery to create a basic web image carousel effect_jquery

First take a look at the effect:

That’s it, no screenshots~

Carousel effect analysis:
The carousel effect can be roughly divided into three parts: carousel images (pictures or containers), buttons that control the display of carousel images (left and right buttons, and index buttons (such as the number buttons at the top of the effect image above) ), displaying carousel images in turn at regular intervals.
Display of carousel images: The carousel images that need to be displayed are displayed, and the carousel images that do not need to be displayed are hidden; usually these carousel images are overlapped together in a positioning manner, and one carousel image is displayed at a time.
Control button: When the mouse is clicked or moved over the index button, the carousel image corresponding to the index position is displayed; the up and down buttons are responsible for controlling the display of the previous and next carousel image.
Others: Generally, index buttons have two states: activated and inactive. Automatic carousing should stop when the mouse moves over the carousel image, and start when the mouse leaves.

Notes on carousel effect implementation:
jquery provides a wealth of selectors and methods for selecting elements, which greatly simplifies our development. For example, $(".slider-item").filter(".slider-item-selected") selects the current The active index button.
The switching display effect of the two carousel images is achieved through jquery's fadeOut() and fadeIn() methods. For specific usage, please refer to jquery's API;
Implementation of CSS transparent background: background: rgba(0, 0, 0, 0.2); filter: progid:DXImageTransform.Microsoft.gradient(startColorstr=#33000000,endColorstr=#33000000); (You can refer to the reference information below), compatible Most major browsers include IE; why not use opacity? Because opacity will make the text transparent (child elements will also be transparent).
HTML skeleton is important, the result of the html you write should be good.

Code part:

HTML:

<pre name="code" class="html"><div class="slider">

 <div class="slider-extra">
 <ul class="slider-nav">
  <li class="slider-item">1</li>
  <li class="slider-item">2</li>
  <li class="slider-item">3</li>
  <li class="slider-item">4</li>
 </ul>
 <div class="slider-page">
  <a class="slider-pre" href="javascript:;;"><</a>
  <a class="slider-next" href="javascript:;;">></a>
 </div>
 </div>
</div>

CSS:

* {
 padding: 0px;
 margin: 0px;
}
a {
 text-decoration: none;
}
ul {
 list-style: outside none none;
}
.slider, .slider-panel img, .slider-extra {
 width: 650px;
 height: 413px;
}
.slider {
 text-align: center;
 margin: 30px auto;
 position: relative;
}
.slider-panel, .slider-nav, .slider-pre, .slider-next {
 position: absolute;
 z-index: 8;
}
.slider-panel {
 position: absolute;
}
.slider-panel img {
 border: none;
}
.slider-extra {
 position: relative;
}
.slider-nav {
 margin-left: -51px;
 position: absolute;
 left: 50%;
 bottom: 4px;
}
.slider-nav li {
 background: #3e3e3e;
 border-radius: 50%;
 color: #fff;
 cursor: pointer;
 margin: 0 2px;
 overflow: hidden;
 text-align: center;
 display: inline-block;
 height: 18px;
 line-height: 18px;
 width: 18px;
}
.slider-nav .slider-item-selected {
 background: blue;
}
.slider-page a{
 background: rgba(0, 0, 0, 0.2);
 filter: progid:DXImageTransform.Microsoft.gradient(startColorstr=#33000000,endColorstr=#33000000);
 color: #fff;
 text-align: center;
 display: block;
 font-family: "simsun";
 font-size: 22px;
 width: 28px;
 height: 62px;
 line-height: 62px;
 margin-top: -31px;
 position: absolute;
 top: 50%;
}
.slider-page a:HOVER {
 background: rgba(0, 0, 0, 0.4);
 filter: progid:DXImageTransform.Microsoft.gradient(startColorstr=#66000000,endColorstr=#66000000);
}
.slider-next {
 left: 100%;
 margin-left: -28px;
}

JavaScript:

$(document).ready(function() {
 var length,
 currentIndex = 0,
 interval,
 hasStarted = false, //是否已经开始轮播
 t = 3000; //轮播时间间隔
 length = $('.slider-panel').length;
 
 //将除了第一张图片隐藏
 $('.slider-panel:not(:first)').hide();
 //将第一个slider-item设为激活状态
 $('.slider-item:first').addClass('slider-item-selected');
 //隐藏向前、向后翻按钮
 $('.slider-page').hide();
 
 //鼠标上悬时显示向前、向后翻按钮,停止滑动，鼠标离开时隐藏向前、向后翻按钮，开始滑动
 $('.slider-panel, .slider-pre, .slider-next').hover(function() {
 stop();
 $('.slider-page').show();
 }, function() {
 $('.slider-page').hide();
 start();
 });
 
 $('.slider-item').hover(function(e) {
 stop();
 var preIndex = $(".slider-item").filter(".slider-item-selected").index();
 currentIndex = $(this).index();
 play(preIndex, currentIndex);
 }, function() {
 start();
 });
 
 $('.slider-pre').unbind('click');
 $('.slider-pre').bind('click', function() {
 pre();
 });
 $('.slider-next').unbind('click');
 $('.slider-next').bind('click', function() {
 next();
 });
 
 /**
 * 向前翻页
 */
 function pre() {
 var preIndex = currentIndex;
 currentIndex = (--currentIndex + length) % length;
 play(preIndex, currentIndex);
 }
 /**
 * 向后翻页
 */
 function next() {
 var preIndex = currentIndex;
 currentIndex = ++currentIndex % length;
 play(preIndex, currentIndex);
 }
 /**
 * 从preIndex页翻到currentIndex页
 * preIndex 整数，翻页的起始页
 * currentIndex 整数，翻到的那页
 */
 function play(preIndex, currentIndex) {
 $('.slider-panel').eq(preIndex).fadeOut(500)
  .parent().children().eq(currentIndex).fadeIn(1000);
 $('.slider-item').removeClass('slider-item-selected');
 $('.slider-item').eq(currentIndex).addClass('slider-item-selected');
 }
 
 /**
 * 开始轮播
 */
 function start() {
 if(!hasStarted) {
  hasStarted = true;
  interval = setInterval(next, t);
 }
 }
 /**
 * 停止轮播
 */
 function stop() {
 clearInterval(interval);
 hasStarted = false;
 }
 
 //开始轮播
 start();
});

The first is the initialization part: hide all pictures except the first carousel picture, hide the forward and backward buttons, and make the first index button active.
Event part: Use jquery's hover() to bind the event processing when the mouse is hovering and leaving, and jquery's bind() method to bind the mouse click event to handle forward, backward, and
Carousel control: pre(), next(), play(), start() starts automatic carousel, stop() stops automatic carousel.
The above js is relatively loosely written, has a poor structure, is laborious to read, is not easy to use, and has a high degree of coupling. The next article will give a pure jquery carousel plug-in, which can customize various effects, convenient configuration and extensibility.

The following is the overall code:
index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>jquery轮播效果图 - by RiccioZhang</title>
<script type="text/javascript" src="scripts/jquery-1.9.1.js"></script>
<style type="text/css">
 * {
 padding: 0px;
 margin: 0px;
 }
 a {
 text-decoration: none;
 }
 ul {
 list-style: outside none none;
 }
 .slider, .slider-panel img, .slider-extra {
 width: 650px;
 height: 413px;
 }
 .slider {
 text-align: center;
 margin: 30px auto;
 position: relative;
 }
 .slider-panel, .slider-nav, .slider-pre, .slider-next {
 position: absolute;
 z-index: 8;
 }
 .slider-panel {
 position: absolute;
 }
 .slider-panel img {
 border: none;
 }
 .slider-extra {
 position: relative;
 }
 .slider-nav {
 margin-left: -51px;
 position: absolute;
 left: 50%;
 bottom: 4px;
 }
 .slider-nav li {
 background: #3e3e3e;
 border-radius: 50%;
 color: #fff;
 cursor: pointer;
 margin: 0 2px;
 overflow: hidden;
 text-align: center;
 display: inline-block;
 height: 18px;
 line-height: 18px;
 width: 18px;
 }
 .slider-nav .slider-item-selected {
 background: blue;
 }
 .slider-page a{
 background: rgba(0, 0, 0, 0.2);
 filter: progid:DXImageTransform.Microsoft.gradient(startColorstr=#33000000,endColorstr=#33000000);
 color: #fff;
 text-align: center;
 display: block;
 font-family: "simsun";
 font-size: 22px;
 width: 28px;
 height: 62px;
 line-height: 62px;
 margin-top: -31px;
 position: absolute;
 top: 50%;
 }
 .slider-page a:HOVER {
 background: rgba(0, 0, 0, 0.4);
 filter: progid:DXImageTransform.Microsoft.gradient(startColorstr=#66000000,endColorstr=#66000000);
 }
 .slider-next {
 left: 100%;
 margin-left: -28px;
 }
</style>
<script type="text/javascript">
 $(document).ready(function() {
 var length,
  currentIndex = 0,
  interval,
  hasStarted = false, //是否已经开始轮播
  t = 3000; //轮播时间间隔
 length = $('.slider-panel').length;
 
 //将除了第一张图片隐藏
 $('.slider-panel:not(:first)').hide();
 //将第一个slider-item设为激活状态
 $('.slider-item:first').addClass('slider-item-selected');
 //隐藏向前、向后翻按钮
 $('.slider-page').hide();
 
 //鼠标上悬时显示向前、向后翻按钮,停止滑动，鼠标离开时隐藏向前、向后翻按钮，开始滑动
 $('.slider-panel, .slider-pre, .slider-next').hover(function() {
  stop();
  $('.slider-page').show();
 }, function() {
  $('.slider-page').hide();
  start();
 });
 
 $('.slider-item').hover(function(e) {
  stop();
  var preIndex = $(".slider-item").filter(".slider-item-selected").index();
  currentIndex = $(this).index();
  play(preIndex, currentIndex);
 }, function() {
  start();
 });
 
 $('.slider-pre').unbind('click');
 $('.slider-pre').bind('click', function() {
  pre();
 });
 $('.slider-next').unbind('click');
 $('.slider-next').bind('click', function() {
  next();
 });
 
 /**
  * 向前翻页
  */
 function pre() {
  var preIndex = currentIndex;
  currentIndex = (--currentIndex + length) % length;
  play(preIndex, currentIndex);
 }
 /**
  * 向后翻页
  */
 function next() {
  var preIndex = currentIndex;
  currentIndex = ++currentIndex % length;
  play(preIndex, currentIndex);
 }
 /**
  * 从preIndex页翻到currentIndex页
  * preIndex 整数，翻页的起始页
  * currentIndex 整数，翻到的那页
  */
 function play(preIndex, currentIndex) {
  $('.slider-panel').eq(preIndex).fadeOut(500)
  .parent().children().eq(currentIndex).fadeIn(1000);
  $('.slider-item').removeClass('slider-item-selected');
  $('.slider-item').eq(currentIndex).addClass('slider-item-selected');
 }
 
 /**
  * 开始轮播
  */
 function start() {
  if(!hasStarted) {
  hasStarted = true;
  interval = setInterval(next, t);
  }
 }
 /**
  * 停止轮播
  */
 function stop() {
  clearInterval(interval);
  hasStarted = false;
 }
 
 //开始轮播
 start();
 });
</script>
</head>
<body>
 <div class="slider">
 <div class="slider-extra">
  <ul class="slider-nav">
  <li class="slider-item">1</li>
  <li class="slider-item">2</li>
  <li class="slider-item">3</li>
  <li class="slider-item">4</li>
  </ul>
  <div class="slider-page">
  <a class="slider-pre" href="javascript:;;"><</a>
  <a class="slider-next" href="javascript:;;">></a>
  </div>
 </div>
 </div>
</body>
</html>

At this point, a simple jquery carousel effect is completed. Of course, there are still many areas for improvement.

Use plugins
The above effect looks satisfactory. The only drawback is that every time you need the carousel effect, you have to copy and paste the code. If some parts need to be modified (for example: the animation effect during the carousel, the previous The article uses jquery's fade-in and fade-out effect. If it is changed to a sliding effect, it is inevitable to modify the js code), then the js code needs to be modified. The js code for the jquery carousel effect I wrote is not familiar with the program. For programmers, it is indeed difficult to modify these js. One of the goals of the carousel plug-in is that the plug-in can be flexibly configured (not just the plug-in in this article). Programmers only need to write a small amount of code to implement rich functions, which is of course a good thing. The html and css parts of the carousel plug-in in this article need to be written by programmers themselves, while the js to achieve the effect only requires a small amount of writing.
The zslider plug-in we use here is open source on GitHub:
github:https://github.com/ricciozhang/zslider_v1
Well, let’s look at the code:

(function($, window, document) { 
  //---- Statics 
  var DEFAULT_ANIMATE_TYPE = 'fade',  
    ARRAY_SLICE = [].slice, 
    ARRAY_CONCAT = [].concat 
    ; 
   
  //---- Methods 
  function concatArray() { 
    var deep = false, 
      result = []; 
    if(arguments.length > 0 &&  
        arguments[arguments.length - 1] === true) { 
      deep = true; 
    } 
    for(var i = 0; i < arguments.length; i++) { 
      if(!!arguments[i].length) { 
        if(deep) { 
          for(var j = 0; j < arguments[i].length; j++) { 
            //recursive call 
            result = ARRAY_CONCAT.call(result,  
                concatArray(arguments[i][j], true)); 
          } 
        } else { 
          result = ARRAY_CONCAT.call(result, arguments[i]); 
        } 
      } else if(i != arguments.length - 1 ||  
          (arguments[arguments.length - 1] !== true && 
              arguments[arguments.length - 1] !== false)) { 
        result.push(arguments[i]); 
      } 
    } 
    return result; 
  } 
 
  //----- Core 
  $.fn.extend({ 
    zslider: function(zsliderSetting, autoStart) { 
      var itemLenght = 0, 
        currItemIndex = 0, 
        started = false, 
        oInterval = {}, 
        setting = { 
          intervalTime: 3000, 
          step: 1, 
          imagePanels: $(), 
          animateConfig: { 
            atype: 'fade', 
            fadeInSpeed: 500, 
            fadeOutSpeed: 1000 
          }, 
          panelHoverStop: true, 
          ctrlItems: $(), 
          ctrlItemActivateType: 'hover' || 'click', 
          ctrlItemHoverCls: '', 
          flipBtn: {}, 
          panelHoverShowFlipBtn: true, 
          callbacks: { 
            animate: null 
          } 
        }, 
        that = this 
        ; 
       
      //core methods 
      var slider = { 
          pre: function() { 
            var toIndex = itemLenght +  
              (currItemIndex - setting.step) % itemLenght; 
            slider.to(toIndex); 
          }, 
          next: function() { 
            var toIndex = (currItemIndex + setting.step) % itemLenght; 
            slider.to(toIndex); 
          }, 
          to: function(toIndex) { 
            //handle the index value 
            if(typeof toIndex === 'function') { 
              toIndex = toIndex.call(that, concatArray(setting.imagePanels, true),  
                    concatArray(setting.ctrlItems, true), 
                      currItemIndex, step); 
            } 
            if(window.isNaN(toIndex)) { 
              toIndex = 0; 
            } 
            toIndex = Math.round(+toIndex) % itemLenght; 
            if(toIndex < 0) { 
              toIndex = itemLenght + toIndex; 
            } 
             
            var currentPanel = setting.imagePanels.eq(currItemIndex), 
            toPanel = setting.imagePanels.eq(toIndex), 
            currrntCtrlItem = setting.ctrlItems.eq(currItemIndex) 
            toCtrlItem = setting.ctrlItems.eq(toIndex) 
            ; 
            if(!setting.callbacks.animate ||  
                setting.callbacks.animate.call(that,  
                    concatArray(setting.imagePanels, true),  
                      concatArray(setting.ctrlItems, true), 
                        currItemIndex, toIndex) === true) { 
              currrntCtrlItem.removeClass(setting.ctrlItemHoverCls); 
              toCtrlItem.addClass(setting.ctrlItemHoverCls); 
               
              toPanel.fadeIn(setting.animateConfig.fadeInSpeed); 
              currentPanel.fadeOut(setting.animateConfig.fadeOutSpeed); 
            } 
             
            //set the current item index 
            currItemIndex = toIndex; 
          }, 
          start: function() { 
            if(!started) { 
              started = true; 
              oInterval =  
                window.setInterval(slider.next, setting.intervalTime); 
            } 
          }, 
          stop: function() { 
            if(started) { 
              started = false; 
              window.clearInterval(oInterval); 
            } 
          }, 
          isStarted: function() { 
            return started; 
          } 
      }; 
      function initData() { 
        if(zsliderSetting) { 
          var temp_callbacks = zsliderSetting.callbacks; 
           
          $.extend(setting, zsliderSetting); 
          $.extend(setting.callbacks, temp_callbacks); 
           
          itemLenght = setting.imagePanels.length; 
        } 
        //convert to the jquery object 
        setting.imagePanels = $(setting.imagePanels); 
        setting.ctrlItems = $(setting.ctrlItems); 
        setting.flipBtn.container = $(setting.flipBtn.container); 
        setting.flipBtn.preBtn = $(setting.flipBtn.preBtn); 
        setting.flipBtn.nextBtn = $(setting.flipBtn.nextBtn); 
      } 
      function initLook() { 
        //show the first image panel and hide other 
        setting.imagePanels.hide(); 
        setting.imagePanels.filter(':first').show(); 
        //activate the first control item and deactivate other 
        setting.ctrlItems.removeClass(setting.ctrlItemHoverCls); 
        setting.ctrlItems.filter(':first').addClass(setting.ctrlItemHoverCls); 
        $(that).css('overflow', 'hidden'); 
        if(setting.panelHoverShowFlipBtn) { 
          showFlipBtn(false); 
        } 
      } 
      function initEvent() { 
        $(concatArray(setting.imagePanels,  
            setting.flipBtn.preBtn, setting.flipBtn.nextBtn, true)).hover(function() { 
          if(setting.panelHoverStop) { 
            slider.stop(); 
          } 
          if(setting.panelHoverShowFlipBtn) { 
            showFlipBtn(true); 
          } 
        }, function() { 
          slider.start(); 
          if(setting.panelHoverShowFlipBtn) { 
            showFlipBtn(false); 
          } 
        }); 
        if(setting.ctrlItemActivateType === 'click') { 
          setting.ctrlItems.unbind('click'); 
          setting.ctrlItems.bind('click', function() { 
            slider.to($(this).index()); 
          }); 
        } else { 
          setting.ctrlItems.hover(function() { 
            slider.stop(); 
            slider.to($(this).index()); 
          }, function() { 
            slider.start(); 
          }); 
        } 
        setting.flipBtn.preBtn.unbind('click'); 
        setting.flipBtn.preBtn.bind('click', function() { 
          slider.pre(); 
        }); 
        setting.flipBtn.nextBtn.unbind('click'); 
        setting.flipBtn.nextBtn.bind('click', function() { 
          slider.next(); 
        }); 
      } 
      function init() { 
        initData(); 
         
        initLook(); 
         
        initEvent(); 
      } 
       
      function showFlipBtn(show) { 
        var hasContainer = setting.flipBtn.container.length > 0, 
          eles; 
        eles = hasContainer &#63; setting.flipBtn.container : 
          //to the dom array: 
          /*ARRAY_CONCAT.call(ARRAY_SLICE.apply(setting.flipBtn.preBtn), 
              ARRAY_SLICE.apply(setting.flipBtn.nextBtn));*/ 
          concatArray(setting.flipBtn.preBtn,  
                  setting.flipBtn.nextBtn, true); 
        if(show) { 
          $(eles).show(); 
        } else { 
          $(eles).hide(); 
        } 
      } 
       
      init(); 
      if(arguments.length < 2 || !!autoStart){ 
        slider.start(); 
      } 
      return slider; 
    } 
  }); 
})(jQuery, window, document);